pki training v1.5
DESCRIPTION
PKI Training Slide by Sylvain MaretTRANSCRIPT
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Introduction to PKI TechnologyIntroduction to PKI TechnologyVersion 1.5Version 1.5
Elaborated by Sylvain Maret & Cédric Enzler
October 1999
Rev. 1.5: August 2000
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Course Map Day OneCourse Map Day One
◆ Introduction◆ Key Terms
◆ Cryptosystems◆ Services, Mechanisms, Algorithms
◆ Cryptography in History◆ Cryptanalysis◆ Secret-Key Cryptography
◆ AES
◆ Lab exercise 1
Course Map Day OneCourse Map Day One
◆ Public-Key Cryptography◆ RSA◆ Diffie-Hellman
◆ Message Digests◆ Lab exercise 2
◆ Random Numbers◆ Key Length◆ Lab exercise 3
◆ File encryption
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Course Map Day OneCourse Map Day One
◆ Message Authentication Code (MAC, HMAC)◆ Digital Signature
◆ RSA, DSS / DSA, ElGamal
◆ Hybrid Cryptosystems◆ RSA Key Wrapping◆ Diffie-Hellman
◆ Lab exercise 4◆ PGP (encryption and signature)
Course Map Day OneCourse Map Day One
◆ PKCS Standard◆ Smart Card◆ Lab exercise 5
◆ SSH◆ SSH Tunneling
◆ End of day one
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Course Map Day TwoCourse Map Day Two
◆ Questions to day one ?◆ Revision quiz !◆ PKI introduction
◆ Digital certificates
◆ X.509 certificates (Demo)◆ Certificate Revocation (Demo)◆ Certification Authorities◆ RA, LRA
◆ Data Repositories (LDAP)
◆ S/MIME: How it works ?
Course Map Day twoCourse Map Day two
◆ Lab exercise 6◆ S/MIME and LDAP
◆ SSL: How it works ?◆ Lab exercise 7
◆ Web server SSL
◆ Lab exercise 8◆ Client SSL authentication
◆ End of day two
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Course Map Day ThreeCourse Map Day Three
◆ Questions to day two ?◆ Lab exercise 9
◆ Smart Card installation (PKCS #11)
◆ Lab exercise 10◆ Playing the security officer with Keon Certificate
Server
◆ Lab exercise 11◆ Revocation with client SSL authentication
◆ IPSEC: How it works ?
Course Map Day ThreeCourse Map Day Three
◆ Lab exercise 12◆ IPSEC (SecuRemote Checkpoint)
◆ Demo◆ IPSEC Cisco with CEP
◆ Cases study◆ VPN RadGuard◆ Secure Gate
◆ Encryption references sites◆ Open discussion◆ End of day three
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Course ObjectivesCourse Objectives
◆ Understand cryptographic fundamentals and how
cryptographic technology is applied in a Public
Key Infrastructure
◆ Know the elements of Public Key Infrastructure
and how they interact with each other
◆ Understand and be able to describe some of the
practical applications of PKI
◆ Understand why PKI is an attractive technology to
enable e-commerce and enhance security
Lab TopologyLab Topology
LondronLondron RomeRome ParisParis MadridMadrid GeneveGeneve BerlinBerlin Newton: DNS, SSHNewton: DNS, SSH
Cerbere: CA
LDAP, Mail
Cerbere: CA
LDAP, Mail
Ayrton: SSLAyrton: SSL
Router IPsec
Router IPsecCheckpoint fw1Checkpoint fw1
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Lab TopologyLab Topology
◆ Domain name : pki.datelec.com◆ Password : abc123 for all applications◆ Be careful ! You are an administrator◆ Email : [email protected]
◆ Do not forget to change name site for labs!
For Labs, you will work together with a partner(London and Rome for instance)
Lab applicationsLab applications
◆ E-mail◆ Netscape (example labs)◆ Outlook 98◆ Lotus notes
◆ Internet browsers◆ Netscape fortified (domestic)◆ Microsoft Internet Explorer 5.0 export
◆ SSH Client◆ Ldap Browser◆ etc.
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PKI, WHY?PKI, WHY?
◆ The rise of public data networks.
◆ Internet is a new platform for business
relationships: E-business
◆ Business rules need to be “translated” into this
new “language”.
◆ Hope behind PKI: to preserve classical business
rules in this new virtual world.
Drawbacks for EDrawbacks for E -- businessbusiness
◆ Let’s say you have an electronic contract which you need to distribute to another party over the Internet…
◆ With existing Internet tools like www and e-mail you lose a lot compared to paper◆ No assurance that the contract has been signed◆ No guarantee that the contract is authentic◆ No assurance of the contract’s source
◆ Basically, it is worth than the paper where everything is printed on!
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About needs...About needs...
◆ You need to know who you are dealing with (Authentication)
◆ You need to keep private things private (Confidentiality)
◆ You need to make sure that people do not cheat (Non-Repudiation)
◆ You need to be sure that information has not been altered (Integrity)
If PKI is the answer thenIf PKI is the answer then ……
What is the question?
On the Internet no one knows you're a dog!
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Key TermsKey Terms
◆ A message will be defined as plaintext or cleartext
◆ The process of disguising a message to hide its substance is encryption
◆ The encrypted message is referred to as ciphertext
◆ Decryption is the process turning ciphertext back into plaintext
Key TermsKey Terms
◆ Cryptography is the science allowing messages to be kept secure
◆ Cryptoanalysis is the art and science of breaking ciphertext
◆ Cryptology is the mathematics field
◆ Cryptologist are theoretical mathematicians
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CryptosystemsCryptosystems
◆ A cryptosystem is a collection of cryptographic algorithms, cryptographic keys, and all possible plaintexts and theirs corresponding ciphertexts.
Security ServicesSecurity Services
◆ Authentication : Provides the assurance of someone’s identity
◆ Confidentiality : Protects against disclosure to unauthorized identities
◆ Non-Repudiation : Protects against communications originator to later deny it
◆ Integrity : Protects from unauthorized data alteration
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Security MechanismsSecurity Mechanisms
◆ Three basic building blocks are used:◆ Encryption is used to provide confidentiality and
integrity protection◆ Digital Signatures are used to provide
authentication, integrity protection and non-repudiation
◆ Checksums / hash algorithms are used to provide integrity protection and can provide authentication
One or more security mechanisms are combined to provide a security service
Cryptography AlgorithmsCryptography Algorithms
◆ All Cryptosystems are based on only three algorithms:◆ 1 - Secret-Key algorithms◆ 2 - Public-Key algorithms◆ 3 - Message-Digest algorithms
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Services, Mechanisms, AlgorithmsServices, Mechanisms, Algorithms
A typical security protocol provides one or more services
Services
Mechanisms
Algorithms
Services are built from MechanismsMechanisms are implemented using Algorithms
SSL, IPSEC, TLS, SSH, etc...SSL, IPSEC, TLS, SSH, etc...
SignaturesSignatures EncryptionEncryption HashingHashing
DSADSA RSARSA RSARSA DESDES SHASHA MD5MD5
Security Protocol LayersSecurity Protocol Layers
Application
Presentation
Session
Transport
DataLink
Physical
Application
Presentation
Session
Transport
Network
DataLink
Physical
Network
S/MIME, PGP
SSL, TLS, SSH
IPSEC
Hardware link encryption
The further down you go, the more transparent it isThe further up you go, the easier it is to deploy
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Cryptography in HistoryCryptography in History
◆ 2000 B.C. Hieroglyphics◆ Cryptography as an Art
◆ Ancient Chinese◆ First to transform messages in Ideographs for privacy
◆ India◆ First “Networks spies” using phonetics encryption
(Javanese or reverse speaking)
◆ Mesopotamia◆ Numbers associate to letters (cuneiform table)
Cryptography in HistoryCryptography in History
◆ ATBASH cipher: In the Bible ◆ ABCDEFGH… (clear)◆ ZYXWVU…(encrypted)
◆ Skytale Cipher (Greek)◆ key: stick◆ papyrus enrolled
◆ Polybius square (Greek)
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Cryptography in HistoryCryptography in History
◆ Runiques Stones by Vikings (Arts)
Cryptography in HistoryCryptography in History
◆ World War II:◆ Electromechanical cryptography◆ Rotor based machine transforming plaintext into
ciphertext, using electrical signals as encryption key◆ Example: Enigma machine used by Germans◆ Ciphers were not new, but their processing was…
◆ 1970-today:◆ New ciphers: based on numbers properties issued from
Mathematical theories◆ RSA: Prime numbers factorization◆ Diffie-Hellman: discrete logarithm◆ ECDSA: Elliptic curve cryptography
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CryptanalysisCryptanalysis
◆ Two categories of security levels◆ Computationally secure:
◆ Question of time and money (Brute force attack)◆ (Most of the cryptosystems: DES, 3DES, IDEA,
RSA, DH etc.)
◆ Unconditionally secure:◆ Can “never” be broken independently of the
resources◆ One-time pads
Several Cryptanalytic AttacksSeveral Cryptanalytic Attacks
◆ Ciphertext only◆ Brute force attack and dictionary attacks on keys
◆ Chosen ciphertext◆ Start from a known ciphertext and try to appear as
someone else to get information from others behavior
◆ Known Plain ciphertext◆ Derive the key from knowledge of both plain and
ciphertext
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SecretSecret --Key CryptographyKey Cryptography
◆ Use a secret key to encrypt a message into a ciphertext
◆ Use the same key to decrypt the ciphertext into the original message
◆ Secret-key cryptography is referred also as symmetric cryptography or conventional cryptography
◆ The secret key is also known as session key or bulk encryption key
SecretSecret --Key CryptographyKey Cryptography
◆ Let us imagine Alice and Bob who use Secret-Key to protect their messages
PlaintextPlaintext PlaintextPlaintextCiphertextCiphertext
Secret-KeySecret-Key
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SecretSecret --Key CryptographyKey Cryptography
◆ How to share the Secret-Key ?◆ Alice and Bob can use the phone, fax, a meeting
point, etc.
◆ But!?:◆ Could someone steal the key?◆ How to proceed without partner knowledge?
SecretSecret --Key CryptographyKey Cryptography
◆ The Advantages◆ Implementation is efficient to encrypt large volume
of data (100 to 1’000 faster than Public-Key Cryptography)
◆ Simple to implement in either software or hardware◆ Most of the algorithms are well know and secure◆ Seem to be safe to brute force attack◆ Widely used
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SecretSecret --Key CryptographyKey Cryptography
◆ The Disadvantages◆ Hard to share Secret-Keys
◆ Large number of keys◆ No non-repudiation (Signature)◆ Subject to interception (Secret-Key)
SecretSecret --Key CryptographyKey Cryptography
◆ Number of needed keys◆ Suppose Alice, Bob and Chris want to use Secret-
Key Cryptography!◆ They need only 3 keys
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SecretSecret --Key CryptographyKey Cryptography
◆ Increase of keys number◆ Suppose they want to add Dawn and Eric
◆ Now they need ten keys
SecretSecret --Key CryptographyKey Cryptography
◆ If n persons want to communicates we have this formula:◆ Key’s number = ((n)*(n-1)) / 2
◆ As example: A company of 60’000 people = 1’799’970’000 keys!
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SecretSecret --Key CryptographyKey Cryptography
◆ Block cipher: Encrypts data in predefined block size◆ Most well-known ciphers are block ciphers
◆ Stream cipher: Encrypts data stream, one-bit at the time◆ Only few algorithms use it
SecretSecret --Key CryptographyKey Cryptography
◆ Common Secret-Key Ciphers◆ DES◆ Triple DES (3DES)◆ RC2
◆ IDEA◆ Blowfish◆ CAST-128◆ Skipjack
◆ RC4 (Stream cipher)◆ etc.
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SecretSecret --Key CryptographyKey Cryptography
◆ DES◆ Data Encryption Standard (1973) by IBM◆ World Standard for 20 years◆ DES was broken in 22 hours (DES challenge III,
January 18th, 1999)◆ Key size = 56 bits◆ Block cipher
◆ Recommendation: should be replaced by 3DES for high confidentiality requirements !
http://www.rsa.com/rsalabs/challenges/
SecretSecret --Key CryptographyKey Cryptography
◆ Triple DES (3DES)◆ Block cipher
◆ Encrypt + decrypt + encrypt with 2 (112 bits) or 3 (168 bits) DES keys
◆ DES’s replacement for Banking (1998)
◆ Recommendation: Use it for high confidentiality!
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SecretSecret --Key CryptographyKey Cryptography
◆ RC2◆ Designed by Ron Rivest from RSA ◆ Block cipher◆ Key size = up to 2048
◆ Encryption speed: independent from the key size◆ Trade secret from RSA, posted on the net in 1996◆ Designed as a DES’ replacement◆ Faster than DES
◆ Recommendation: like DES but faster!
SecretSecret --Key CryptographyKey Cryptography
◆ CAST-128◆ Designed by C.Adams and S. Tavares (1993)
◆ Block cipher◆ Key size = 128 bits◆ Used in PGP 5.x
◆ Recommendation: unknown
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SecretSecret --Key CryptographyKey Cryptography
◆ IDEA◆ International Data Encryption Algorithm ◆ Designed by X.Lai and J. Massey (ETH Zurich) in
1990
◆ Block cipher◆ Key size = 128 bits◆ More efficient than DES for software
implementation
◆ Used in PGP
◆ Recommendation: Better than DES
SecretSecret --Key CryptographyKey Cryptography
◆ Blowfish◆ Designed by B. Schneier in 1993
◆ Optimized for high-speed execution on 32-bit processors
◆ Block cipher◆ Key size = up to 448 bits key
◆ Recommendation: Use for fast performances and with a maximum key size
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SecretSecret --Key CryptographyKey Cryptography
◆ Skipjack◆ Designed by NSA (National Security Agency)
◆ Block cipher◆ Key size = 80 bits
◆ Recommendation: Inadequate for long term security (key size too short)
SecretSecret --Key CryptographyKey Cryptography
◆ GOST◆ Acronym for “GOsudarstvennyi STandard”
◆ Russian answer to DES◆ Key size = 256 bits
◆ Recommendation: Incompletely specified to give an answer...
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SecretSecret --Key CryptographyKey Cryptography
◆ RC4◆ Designed by Ron Rivest from RSA ◆ Stream cipher◆ Key size = up to 2048 bits◆ Optimized for fast software implementation◆ Trade secret from RSA, posted on the net in 1994◆ Very fast◆ Used in SSL, Lotus Note, Windows password
encryption, Oracle etc.
◆ Recommendation: Highly recommended for long keys (>40 bits)
SecretSecret --Key CryptographyKey Cryptography
◆ Many, many others◆ There is no good reason not to use one of above
proven algorithms!
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SecretSecret --Key Relative PerformanceKey Relative Performance
RC4Blowfish, CAST-128SkipjackDES, IDEA, RC23DES, GOST
FAST
SLOW
AESAES
◆ National Institute of Standard and Technology expressed a formal call for algorithm on 09.1997
◆ The aim is to define the “next century’s”symmetric encryption standard or Advanced Encryption Standard
◆ AES1 conf. (08.98): 15 potential candidates ◆ AES2 conf. (03.99): 5 retained candidates◆ Final choice expected for summer 2001
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AES candidatesAES candidates
◆ MARS (IBM)◆ RC6 (RSA Laboratories)◆ Rijndael (J. Daemen, V. Rijmen)◆ Serpent (R. Anderson, E. Biham, L. Knudsen)◆ Twofish (B. Schneier - Counterpane)
AES requirementsAES requirements
◆ Block cipher of minimum 128 bits◆ Must implement symmetric keys of 128, 192,
256 bits ◆ Must be efficient on software and hardware
basis (high speed encryption)
Http://www.counterpane.com/aes-comparison.html
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SecretSecret --Key CryptographyKey Cryptography
◆ Use a symmetric encryption to encrypt a text file (DES and IDEA)
◆ Time: 15 minutes◆ P.27
PublicPublic --Key CryptographyKey Cryptography
◆ Use two distinct keys, one public and one private◆ The private is kept secret◆ The public can be freely shared◆ Referred as asymmetric cryptography◆ A public-key and its corresponding key are
mathematically related◆ A public-key and its associated private-key are
called a key-pair
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PublicPublic --Key CryptographyKey Cryptography
◆ A message encrypted with a public-key can be only decrypted by the private-key
◆ A message encrypted with a private-key can be only decrypted by the public-key (Signature)
PublicPublic --Key CryptographyKey Cryptography
◆ Suppose Alice wants to send a message to Bob using Public-Key Cryptography
PlaintextPlaintext PlaintextPlaintextCiphertextCiphertext
Bob’s public keyBob’s public key Bob’s private keyBob’s private key
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PublicPublic --Key CryptographyKey Cryptography
◆ How to obtain the public-key ?◆ Any publishing way can be used to get the public-
key (Directory servers, Phone, Web server, Newspapers etc.)
◆ No more confidentiality issues in key distribution
PublicPublic --Key CryptographyKey Cryptography
◆ Advantages◆ No secret sharing◆ Fewer keys◆ No prior relationship needed
◆ Easier to administrate◆ Offers useful mechanisms like digital signature
(offering non repudiation)
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PublicPublic --Key CryptographyKey Cryptography
◆ Disadvantages◆ Not efficient (slow) to encrypt large volume of data
◆ Keys need to be much longer than with secret-key encryption
◆ Impossible to encrypt a plaintext with size > key
Types of publicTypes of public --key algorithmkey algorithm
◆ A public-key algorithm is reversible if encryption and decryption can be processed with either a private or a public-key
◆ A public-key algorithm is irreversible if a private-key is mandatory for encryption
◆ Key exchange algorithm: neither used for encryption nor decryption (Diffie-Hellman)
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RSARSA
◆ Inventors: R ivest, Shamir, Adleman in 1977◆ Most popular◆ Provide confidentiality, digital signature and
key exchange◆ Key length up to 4096◆ Plaintext length < Key length◆ Ciphertext size = Key size
RSARSA
◆ RSA is protected by a patent. Patent expires on 20th September 2000
◆ Relies on irreversible mathematics functions (Prime numbers)
PDAs, WAPs: RSA Multi-Prime
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DiffieDiffie --HellmanHellman
◆ Published in 1976 by W. Diffie and M. Hellman◆ Oldest known public-key cryptosystem◆ Key agreement algorithm
◆ Enables secret-key exchange without prior knowledge
◆ Agrees on shared secret used in conjunction with a secret-key Cryptosystem (DES, 3DES, IDEA, etc.)
DiffieDiffie --HellmanHellman : How it works ?: How it works ?
Share Secret KeyShare Secret Key Share Secret KeyShare Secret Key
Alice’sprivate key
Bob’sprivate key
Alice’spublic key
Bob’spublic key
=
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DSADSA
◆ Compliant to D igital Signature Standard (DSS)◆ Published in 1994◆ Irreversible algorithm (encryption with private
key only)◆ Used in Digital signature only◆ Performance tuned for smart cards
Comparative PublicComparative Public --Key tableKey table
Algorithm Type
DSA Digital Signature
El-Gamal Digital Signature
RSA ConfidentialityDigital SignatureKey exchange
Diffie-Hellman Key exchange
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MessageMessage --Digest AlgorithmsDigest Algorithms
◆ Take a variable-length message and produce a fixed-length digest as output
◆ The fixed-length output is called the message digest, a digest or a hash
◆ A message-digest algorithm is also called a one-way hash algorithm or a hash algorithm
MessageMessage --Digest AlgorithmsDigest Algorithms
Hash Function
Input
Message
Input
Message
Fixed-length DigestFixed-length Digest
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MessageMessage --Digest AlgorithmsDigest Algorithms
◆ Message-Digest Algorithms properties required to be cryptographically secure◆ It must not be feasible to determine the input
message based on its digest
◆ It must not be possible to find an arbitrary message that has a particular, desired digest
◆ It should be impossible to find two messages that have the same digest (collision)
◆ It should be very sensitive to input message changes
MessageMessage --Digest AlgorithmsDigest Algorithms
◆ Some Common Message-Digest Algorithms◆ MD2: 128-bit-output, deprecated, by Ronald Rivest◆ MD4: 128-bit-output, broken, by Ronald Rivest◆ MD5: 128-bit-output, weaknesses, by Ronald
Rivest◆ SHA-1: 160-bit-output, NSA-Designed◆ RIPEMD-160: 160-bit-output◆ Haval: 128 to 256 bit-output (3 to 5 Passes)
◆ CRC-32: 32-bit-output
◆ Recommendation: Use SHA-1
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MessageMessage --Digest AlgorithmsDigest Algorithms
◆ Message-Digest at work◆ Creation of digital signatures
◆ Creation of MAC, HMAC◆ Creation of secret-key with a passphrase◆ File checksum (FTP server, Patches, etc.)◆ FIA (File Integrity Assessment like Tripwire)
Powerful tool to detect small changes
MessageMessage --Digest AlgorithmsDigest Algorithms
◆ Use Message-Digest Algorithms to compute a file’s digest (MD5 and SHA-1)
◆ Time: 15 minutes◆ p.31
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Random NumbersRandom Numbers
◆ Random numbers are usually required to generate cryptographic keys or challenge.
◆ Two main categories◆ (PRNG) Pseudo Random Number Generator uses
a deterministic algorithm to generate a pseudo random number based on a seed (mouse, keyboard, etc..)
◆ A random number generator generates truly unpredictable numbers. Based generally on special hardware (white noise, radioactive-decay, etc…)
Random NumbersRandom Numbers
◆ A very secure cryptosystem can be broken if it relies on random numbers that can be guessed◆ Netscape browser using SSL broken!
◆ Some PRNG◆ Yarrow from B. Schneier◆ CryptPack
◆ etc.
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Keys LengthKeys Length
◆ To break a secret-key cryptosystem with “no weakness”, an attacker must try each possible key. This is called a brute force attack
◆ To break a public-key cryptosystem an attacker should use “smarter” brute force attack based on mathematics
◆ Key space dimension = 2n (n:keylength)
What is the right key size ?What is the right key size ?
◆ The goals of cryptography are to make the value of encrypted information less than the money spent to decrypt it !
◆ the value of information usually decreases over time
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RSARSA’’ss Challenge on DES (III)Challenge on DES (III)
◆ Method: splitting the Key space for distributed Brute Force Attack (space dimension = 2n , where n is the key-length)
◆ Starting date: 18.01.99. Ending: 22h15 min. later…
◆ Brute Force Attack frequency: 245 Billions keys/sec.
◆ Platforms: Cray/Sun/SGI/Pentium etc..
RSARSA’’ss Challenge on RSAChallenge on RSA --155155
◆ Key-length: 512 bits = 155 digits◆ Method: Prime number factorization◆ Starting Date: August 99. Ending: 5 months
later◆ Time: 35.7 CPU years◆ Platforms: SGI/Sun/Pentium etc.
◆ 292 computers
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KeysKeys ’’ time of lifetime of life
◆ Most of the time, session keys are changing (IPSec, etc.)◆ to enforce security
◆ Can be triggered by time or by encrypted data quantity
PublicPublic --Key Key vsvs SecretSecret --keykey
Secret-key (bits) Public-Key (bits)40 274
56 384
64 512
80 768
96 1024
112 1792
120 2048
128 2304
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Blowfish Advanced CS: How it works ?Blowfish Advanced CS: How it works ?
Blowfish Advanced CSBlowfish Advanced CS
◆ File encryption software using symmetric encryption
◆ Used secret-key from a password or a “key-disk”
◆ Support key splitting◆ Wipes sensitive information◆ Used secret-key ciphers like:
◆ Blowfish◆ 3DES
◆ Twofish
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Blowfish Advanced CSBlowfish Advanced CS
◆ Use SHA-1 to generate secret-key from a password
◆ Use random (PRNG) to create the key file and to overwrite (wiping) data
File EncryptionFile Encryption
◆ Setup a file’s encryption software to protect sensitive information
◆ Time: 20 min◆ p.38
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Message Authentication CodeMessage Authentication Code
◆ MAC is a fixed-length data item that is send together with a message to prove integrity and origin
◆ Provide authentication and integrity without confidentiality
◆ Also referred as message integrity code (MIC)◆ Most common form is HMAC ( Hashed Mac)◆ Example: HMAC-MD5
Message Authentication CodeMessage Authentication Code
+Secret-Key
Hash Function
Input
Message
Input
Message
HMACHMAC
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Digital SignatureDigital Signature
◆ Digital signature is a data item that guarantees the origin and integrity of a message
◆ The signer of the message uses a signing key◆ The recipient uses a verification key to verify
the origin and integrity◆ Signing key = private-key◆ Verification key = public-key
Digital SignatureDigital Signature
◆ By using his own private key, the signer can not repudiate the fact he has signed the message
◆ This mechanism provide non-repudiation
◆ Think about the difference with MAC …
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Digital Signature: BasicsDigital Signature: Basics
PlaintextPlaintext PlaintextPlaintextCiphertext
(Signature)
Ciphertext
(Signature)
Alice’s private keyAlice’s private key Alice’s public keyAlice’s public key
Simple signature using PRIVATE-key
Digital Signature: How it works?Digital Signature: How it works?
SignatureSignature
PlaintextPlaintext
Alice’s private key
SignatureSignature
Alice’s Public key
MD1 = MD2 ???MD1 = MD2 ???
PlaintextPlaintext
DigestDigest
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Digital SignatureDigital Signature
◆ Why signing a message involves Hashing ?◆ Signature (data item) is too big
◆ Performance (public-key is very slow)◆ Possible attack (known plaintext attack)
Common Signature AlgorithmsCommon Signature Algorithms
◆ RSA◆ Well known◆ Export limitation
◆ DSA◆ Similar to RSA (algebraic properties of numbers)◆ Non-reversible algorithm, suitable for digital
signature only
◆ ElGamal◆ Another cipher for digital signature only
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Hybrid CryptosystemsHybrid Cryptosystems
◆ A Hybrid Cryptosystem combines the best features of both Secret-Key and Public-Key cryptography
◆ Used to exchange session key to initiate a symmetric encryption
◆ Example : PGP, SSL, IPSEC using Diffie-Hellmanor RSA
Example: Example: DiffieDiffie --HellmanHellman and Secretand Secret --Key Key cryptosystemcryptosystem
Share Secret KeyShare Secret Key Share Secret KeyShare Secret Key=
PlaintextPlaintext PlaintextPlaintextCiphertextCiphertext
Asymmetric
Symmetric
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RSA Key wrapping encryptionRSA Key wrapping encryption
◆ Suppose Alice wants to send an encrypted text to Bob across the Internet , using RSA key wrapping
RSA Key wrapping encryptionRSA Key wrapping encryption
◆ How it works ?◆ Alice creates a session key, which is a one-time-
only secret-key◆ Alice encrypts the data with the session key◆ Alice encrypts the session key with Bob’s public-
key
◆ Alice sends the ciphertext + the encrypted session key to Bob
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RSA Key wrapping encryptionRSA Key wrapping encryption
RSA Key wrapping decryptionRSA Key wrapping decryption
◆ How it works ?◆ Bob receives the message from Alice
◆ Bob uses his private-key to recover the temporary session key
◆ Bob uses the session key to decrypt the ciphertext
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RSA Key wrapping decryptionRSA Key wrapping decryption
How sure can Alice be about Bob’s presumed public-key ?
RSA Key wrapping question ?RSA Key wrapping question ?
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Man in the Middle Attack!Man in the Middle Attack!
PGP: How it works ?PGP: How it works ?
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PGP: introductionPGP: introduction
◆ Stands for Pretty Good Privacy◆ By Phil Zimmerman (1991)◆ Worldwide distributed in 1991◆ Provides mail and file encryption/signature◆ Today: PGP 6.5.2◆ Available on many platforms like:
◆ Unix◆ Windows◆ Linux◆ Atari, Macintosh, OS/2 etc.
PGP IntroductionPGP Introduction
◆ Contains a set of algorithms for◆ Message digest:
◆ MD5, SHA1 and RIPEMD
◆ Public-key:◆ RSA, DSA
◆ Secret-key:◆ DES, 3DES, CAST-128 and IDEA
◆ Data compression: LZH
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Original PGP signatureOriginal PGP signature
◆ Using RSA and MD5 for example
Quiz!Quiz!
56
Original PGP encryptionOriginal PGP encryption
◆ Encryption based on RSA key wrapping
Original PGP decryptionOriginal PGP decryption
◆ Decryption based on RSA key wrapping
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Quiz!Quiz!
PGP todayPGP today
◆ To enforce security, PGP offers today DSS
and DH key exchange
◆ Support for x.509 certificate as well
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PGP Trust modelPGP Trust model
◆ Originally, PGP trust models were:
◆ Direct trust (hosts mutually and directly trusted)
◆ “Web-of-Trust”
◆ If Alice trusts Bob and Bob trusts Charlie, then Alice
will trust Charlie
◆ In other words…friends of my friends are my friends
◆ Today, hierarchical trust is also possible
Other PGP productsOther PGP products
◆ PGP Phone
◆ to transform a desktop into a secure phone via
real-time encryption
◆ PGP disk
◆ offering privacy to file system
◆ PGP SDK
◆ development kit
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PGPPGP
◆ Use PGP for sending a signed and encrypted
◆ Time: 40 min
◆ P.49
SSH: How it works ?SSH: How it works ?
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SSHSSH
◆ SSH = Secure Shell
◆ Originally developed in 1995 as a secure
replacement for rsh, rlogin,rcp, ftp, telnet
◆ Originally implemented in Finland
◆ Available worldwide
◆ About 3’000’000 users around the world
Http://www.cs.hut.fi/ssh
SSHSSH
◆ Also allows port forwarding (tunneling over SSH)
◆ X11 connection forwarding◆ SSH v2 submitted to IETF◆ Can be run and used in a short space of time◆ Many SSH clients available
◆ Secure CRT◆ F-Secure◆ Java Client
◆ etc.
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SSH: Why ?SSH: Why ?
Attacker with snifferNetwork
Original TCP Packet
Login: rome
Password: abc123
Unix HostUnix Host
Telnet to Unix HostTelnet to Unix Host
SSHSSH--1 Protocol (Hybrid Crypto)1 Protocol (Hybrid Crypto)
TCP
Auth request
SSH
Client Server
DATA
Client performs TCP handshake with the server at port 22 for SSH standard port
Start authentication process. Client send authentication request
Server decrypt the session key with the two private keys. Begin bulk encrypted data exchange. Client encrypts
Server decrypts request, encrypts and sends response
S
Symmetric Encrypteddata
SSHHandshakePublic Key
S
22
Session
The server responds with two keys. Host key 1024 bit RSA and a Server key 768 bit RSA (Generated hourly)
Client verify host key and generate a secret key that is used for bulk encryption then encrypt this secret key twice with Host and Server public keys and send it to the server SSH
62
SSH CiphersSSH Ciphers
◆ SSH v1◆ RSA
◆ DES, 3DES, Blowfish, IDEA
◆ SSH v2◆ Diffie-Hellman for key exchange algorithm◆ DSA, RSA
◆ 3DES, Blowfish, IDEA, Twofish, Arcfour, Cast-128
SSH AuthenticationSSH Authentication
◆ Multiple Authentication mechanisms◆ Static password (protected by SSH encryption)
◆ RSA or DSA authentication (client decrypts challenge from server)
◆ Plug-in authentication (Securid, Radius, ldap, PAM *)◆ “.rhosts or /etc/hosts.equiv” (Based on IP address)
http://www.bg.kernel.org/pub/linux/libs/pam/index.html*
63
SSH Authentication (RSA/DSA)SSH Authentication (RSA/DSA)
◆ Client decrypts “challenge” from server◆ Provides “strong” authentication (client uses
his private-key plus a PIN code)
Server sends encrypted challenge with client’s public key
Client decrypts challenge and sends it to the server
The challenge is chosen randomly
SSH Tunneling modeSSH Tunneling mode
SSH
Server
SSH
Server
HTTP 127.0.0.1 1999HTTP 127.0.0.1 1999
Encrypted SSH tunnel Clear text
Web serverWeb server
DMZ
Corporate Net
SSH
Client
SSH
Client
64
SSHSSH
◆ Setup a SSH client to replace Telnet. Use two authentication mechanisms.
◆ Setup a SSH tunnel◆ Time: 60 min
◆ p. 64
PKCSPKCS
◆ Public Key Cryptographic Standard (PKCS)◆ Standardization of public-key algorithmic, in order to
maintain interoperability◆ Developed by RSA Laboratories, a consortium of
information technology vendors and academic institutions.
◆ Apple◆ Microsoft◆ Compaq◆ Lotus◆ Sun◆ MIT etc.
65
PKCS listPKCS list
◆ #1: Encrypting and signing using RSA public key cryptosystem◆ #3: Key agreement with Diffie-Hellman key exchange
◆ #5: Encrypting with a secret key derived from a password
◆ #7: Syntax for message with digital signature
◆ #8: Format for private key information
◆ #9: Attribute type for use in other PKCS standard◆ #10: Syntax for certification request
◆ #11: Define a cryptoki programming interface (API for smart cards)
◆ #12: Portable format for storing and transporting private keys
◆ #13: Encrypting and signing data using elliptic curves cryptography
◆ #14: Standard for pseudo number generation◆ #15: Standard to store credentials on tokens
Smart CardSmart Card
◆ Smart Cards consist of a chip (processor or/and memory), a contact plate and a piece of plastic (ISO 7810 - 54x85x0.8 mm)
◆ Smart Cards are used for multi-applications◆ GSM, Banking, Medical, E-Commerce, Pay TV, etc…
66
Smart Card and PKISmart Card and PKI
◆ Storing the private-key and/or X.509 certificate on the Smart Card
◆ Provide Strong Authentication◆ Something you have, Something you know
◆ Access protected by a PIN (like credit card)
◆ Types of Smart Card◆ Memory Cards◆ PKI smart cards using Crypto-processor (RSA, etc.)
◆ Some Smart Card are “brute force” protected
Smart Card Standard (interface)Smart Card Standard (interface)
◆ PKCS #11 also call Cryptoki◆ Interface for the communication to Smart Card
◆ Netscape, RSA
◆ PC/SC and their Crypto API◆ http://www.pcscworkgroup.com/◆ Bull, Gemplus, HP, Intel, Microsoft, Schlumberger
Siemens, SUN, Toshiba
67
Smart Card ReaderSmart Card Reader
◆ Keyboard◆ USB◆ Serial◆ PCMCIA◆ Diskette reader◆ SCSI
TodayToday ’’s Smart Card Drawbackss Smart Card Drawbacks
◆ Hardware...◆ Multi-Services rarely used
◆ Users leave Smart Card on the reader
68
End Day OneEnd Day One
Questions Day One ?Questions Day One ?
69
Quiz!Quiz!
◆ Describe Secret-Key ?◆ Advantages / Disadvantages
◆ Describe Public-Key ?◆ Advantages / Disadvantages
◆ Describe Messages Digest ?◆ Describe Digital Signature and verification ?◆ Differences between MAC and signature?◆ Describe two Hybrid Cryptosystems ?◆ Describe a challenge response based
authentication?
PKI introductionPKI introduction
◆ The aim of PKI is to integrate all the previous mechanisms and algorithms into a coherent and efficient structure.
◆ It will answer the following fundamental security needs:◆ Authentication
◆ Confidentiality◆ Non-Repudiation◆ Integrity
◆ The basis of PKI relies on the concept of certificates
70
PKI basis functionPKI basis function
◆ PKI will include at least:◆ One Certificate Authority who delivers certificates
◆ One Directory who stores active Certificates and/or Revoked Certificates
◆ One Registration Authority who allows certificates’enrollment
◆ One centralized Management
Remember Alice, Bob and Charlie...Remember Alice, Bob and Charlie...
Bob has no proof of the “link” between Alice’s public-keys and her identities
So What ?
71
Third Trusted PartyThird Trusted Party
Implicit Trust
No more Charly
Trusted Authority
Direct Trust Direct Trust
Digital CertificatesDigital Certificates
◆ A public-key certificate is a bond between an entity’s public-key and one entity
◆ The entity can be:◆ A person
◆ A role (Manager Director)◆ An organization◆ A piece of hardware (Router, Server, IPSEC, SSL,
etc.)◆ A software process (JAVA Applet)
◆ A file (Image, Databases, etc.)◆ etc.
72
Digital CertificatesDigital Certificates
◆ A Public-key certificate provides assurance that the public-key belongs to the identified entity
◆ A Public-key certificate is also called a digital certificate , digital ID or certificate
◆ The entity identified is referred to as the certificate subject
◆ If the certificate subject is a person, it is referred to as a subscriber
Digital CertificatesDigital Certificates
◆ A certificate is like a passport ...
73
How to obtain a certificateHow to obtain a certificate
◆ As with passports, you give proof of your identity to an official (or trusted) authority.
◆ The authority checks this proof.◆ The authority delivers a signed passport .◆ This procedure is defined as an “enrollment”◆ Instead of “enrolling” for a passport we’ll
enroll for digital certificate.
Digital CertificatesDigital Certificates
◆ Graphical representation of a certificate
74
Demo: certificate viewDemo: certificate view
X.509 Certificate StandardX.509 Certificate Standard
◆ X.509 is a standard for digital certificate by International Telecommunications Union (ITU)
◆ First published in 1988 (V1.0)◆ Version 2.0 (1993) adds two new fields◆ Current version is v3.0 (1996) and allows
additional extension fields
75
X.509 Basic Certificate FieldsX.509 Basic Certificate Fields
◆ Version : X509 version 1,2 and 3◆ Certificate serial number : Integer assigned by
the CA (unique)◆ Signature algorithm identifier : RSA/MD5 etc.◆ Issuer name : name of CA having signed and
issued the certificate◆ Validity period : time interval◆ Subject name : the entity name (this name must
be unique = distinguished name (DN) )
X.509 Basic Certificate FieldsX.509 Basic Certificate Fields
◆ Subject public-key information : contains the public-key plus the parameters
◆ Issuer unique identifier : optional field◆ Subject unique identifier : optional field◆ Extension s: may provide additional data for
specific applications.
And the Certification Authority's Digital Signature
76
SSL X.509 exampleSSL X.509 example
Data and Signature section in human-readable format!
SSL X.509 exampleSSL X.509 example
Here is the same certificate in the 64-byte-encodedformat interpreted by a software
77
How to build a CertificateHow to build a Certificate
CA’sSignature
X.509Fields
Public keyIdentity
etc.
DigitalSignatureProcess
CA
X.509Certificate
Think of it like a credit cardThink of it like a credit card ……
Digital Credit Union
DCUDCUDCUDCU
Andrew NashAndrew Nash
GOOD THRULAST DAY OF 06/9806/98
5867 9506 3461 19205867 9506 3461 1920
AUTHORIZEDSIGNATURE
Andrew K Nash
Validity
Period
Signature
Issuer Name
Subject Name
Public Key
78
How to verify a certificate ?How to verify a certificate ?
◆ Obtain the Signer’s (CA) public-key◆ Pass the X.509 fields into the message digest
algorithm and keep the digest (= your digest 1)◆ Decrypt the Certificate signature with the
Signer’s (CA) public-key. The decrypting plaintext will be the digest (= your digest 2)
◆ Compare the digest 1 with the digest 2◆ Does this match together?
Verifying a certificate?Verifying a certificate?
MD1 = MD2 ???MD1 = MD2 ???CA’sSignature
X.509Fields
Public keyIdentity
etc.
CA’s public keyCA’s public key
79
A few words about CAsA few words about CAs
◆ Entities that issue and manage digital certificates including◆ maintaining ◆ revoking
◆ publishing status information
◆ CAs’ security policy defined in CPS (Certification Practice Statement)◆ Security measures to guarantee CA’s integrity◆ Security measures to check enrollment’s identity
◆ Trust level relies upon CPS and not technology
Few words about CAsFew words about CAs
◆ PKI security relies on CA’s private-key secrecy◆ Should never be acceded◆ Should be backed-up
◆ Solution: store it inside dedicated tamperproof hardware
80
Type of CAsType of CAs
◆ Private CAs:◆ Hold by a private entity (Company, Administration,
the Military)
◆ Public CAs:◆ Verisign, Swisskey, GTE, Thawte, Global-sign,
Certplus, etc.
A CA can be hybrid as for instance“On-site services” of Verisign
Registration Authority (RA)Registration Authority (RA)
◆ A Registration Authority is the entity receiving the certification requests and managing them before sending them to the CA. RA acts as a front end.
◆ As in hybrid CAs, the registration authority can be separate from the CA itself. In this case we talk about Local Registration Authority (LRA)◆ Multiple sites for big companies◆ Distributed environment
81
(L)RA Front End(L)RA Front End
LDAPLDAP
◆ X.500 Directories required more effort and complexity than most companies were prepared to invest
◆ Lightweight Directory Access Protocol was proposed by the Internet community
◆ LDAP uses the X.500 naming conventions but simplifies the way you interact with a directory
82
LDAPLDAP
◆ LDAP is a “front end” that is used to implement simple directory services
◆ An LDAP Server may be implemented over:◆ a full X.500 Directory
◆ a database◆ a flat file◆ Most of structured data set
◆ CA will use LDAP to publishcertificates and CRLs
Demo: browsing Demo: browsing ldapldap
http://www.iit.edu/~gawojar/ldap/
83
Certificate RevocationCertificate Revocation
◆ Certificate Revocation:◆ Mechanism used by the CA to publish and
disseminate revoked certificates
◆ Revocation is triggered in the following cases:◆ Key compromise◆ CA compromise
◆ Cessation of operation◆ Affiliation change ◆ etc...
Certificate RevocationCertificate Revocation
◆ Several data structures exist to publish revocation◆ CRL (Certificate Revocation List)◆ ARL (Authority Revocation List)◆ CRT (Certificate Revocation Trees) by Valicert
◆ Also Online query mechanisms◆ OCSP (Online Certificate Status Protocol)
84
CRLCRL’’ss publication and retrievalpublication and retrieval
◆ Certificate-using applications must be aware of revoked certificates◆ Get CRL via ldap◆ Get CRL via FTP, Http, Https, etc.◆ Check certificate status via OCSP◆ Etc.
◆ Problem to solve: Revocation delay !◆ Not yet fully standardized (Delta CRLs, OCSP
etc.)
CRL Version 2 structureCRL Version 2 structure
VersionSignaturealgorithm
Issuer DN
UpdateDate
NextUpdate
Date
List of revoked certificatesper-certificates extensions
Extensions
85
CRL Version 1 view (text)CRL Version 1 view (text)
CRL Version 1 view (PEM)CRL Version 1 view (PEM)
86
Demo: get a CRLDemo: get a CRL
OSCPOSCP
OCSPResponder
CA
Backend
LDAP
OCSP
FTP, http
others
OCSP overhttp
PKI enableApplications
Pushing Revocation
87
Distinguish NamesDistinguish Names
◆ X.509 certificates bind a Distinguish Name (DN) to a public-key
◆ A DN is a set of name-value pairs, such as uid=cenzler, that uniquely identify an entity
◆ Example: a typical DN of a Datelec employee:◆ C=CH, O=Datelec, OU=Engineering,
L=Geneva, CN=Cedric Enzler, [email protected]
Distinguish NamesDistinguish Names
◆ DNs may include a variety of other name-value pairs (see X.500 standard)
◆ Most CAs are LDAP compliant. Thus, DNs will be used as entries in Directories that support LDAP
88
Single CASingle CA
◆ Until now, we assumed the presence of a unique CA certifying all users. Thus, there’s a direct relation between users and their CA
X509
X509X509
X509X509
X509
Multiple CAs topMultiple CAs top --downdown
◆ Typical CA implementation for large companies
X509 X509
X509X509
X509
X509X509
X509X509X509
Root CA
Subordinate CAs
Subordinate CAs
Certificates
Trust relation
89
TrustTrust
◆ Because a CA has a certificate itself and represents the highest possible trust level, the CA has its self-signed certificate
◆ A self-signed certificate is a Root Certificate or Meta-Introducer
◆ A certificate-using application (any X.509 holders) must trust the Root certificate
◆ Importing a Root certificate into such an application is called Bootstrapping a CA
Bootstrapping must be considered as a very critical operation!
Trusted Root certificatesTrusted Root certificates
◆ Many applications (as http browsers) have already embedded root certificates
90
Demo: Bootstrap Demo: Bootstrap SwisskeySwisskey
Trust architectureTrust architecture
X509 X509
X509 X509
X509
X509 X509X509X509X509
Root CA
CA1
A C
Assume Alice, Bob and Charly are exchanging e-mails
CA2
B
CA3
91
Simple CaseSimple Case
◆ Alice receives Bob’s e-mail and the X.509 certificate
◆ How can Alice check Bob’s certificate?◆ She looks at Bob’s signer◆ Does she know the signer?
◆ Yes: Is it a self-signed?◆ No: Is the upper level CA trusted?
X509
Bob
2
3
X509
Root
X509
CA3
1
More complicated...More complicated...
◆ Alice receives Charly e-mail and the X.509 certific ate◆ How can Alice check Charly certificate?◆ Charly sent intermediary CAs certificates along wit h
his own certificate. This is the “chain of certific ates”◆ Thus, the validation process will be...
X509
CA2X509
Charly
X509
CA1
X509
Root
12
3
4
92
Cross certificationCross certification
X509 X509
X509 X509
X509
X509 X509X509X509X509
X509 X509
X509 X509
X509
X509 X509X509X509X509
A typical case: merging of Certification Islands:
LetLet ’’s be practical!s be practical!
User enrolls for certificate
http://www...http://www...
User mailed retrieval PIN
User retrieves certificate
http://www...http://www...
Admin Approves request
http://www...http://www...
User mailed acknowledgement
Admin mailed notification
RA
CA
User
SecurityOfficer
LDAP
Certificate installed
93
Some X.509 certificate typesSome X.509 certificate types
◆ CA certificate (Root)◆ S/MIME◆ SSL server/client◆ IPSec gateway/client◆ Object signing certificates
◆ Java script◆ Image signature for copyright◆ File detection intrusion (binary certifications)
◆ etc.
PKI StandardsPKI Standards
◆ Some standard organizations:◆ IETF PKI Working Group (PKIX)
◆ ITU◆ SPKI◆ RSA with PKCS
94
PKI VendorsPKI Vendors
Some Public CASome Public CA
95
PKI SummaryPKI Summary
◆ Based on Certificates (X.509)◆ Trusted third party (CA)◆ (L)RA◆ CRL◆ Data repositories◆ Mechanisms and protocols between all these
elements
S/MIME: How it works ?S/MIME: How it works ?
96
S/MIMES/MIME
◆ Secure Multipurpose Internet Mail Exchange◆ Developed by RSA, Microsoft, Lotus, Banyan, and
Connectsoft in 1995◆ Implemented at application layer◆ Build on top of PKCS #7 and PKCS #10◆ Very strong commercial vendor acceptance
◆ Netscape, Microsoft, Lotus, etc.
◆ IETF developed S/MIME v3 (last version)◆ Use X.509 certificates
S/MIMES/MIME
◆ S/MIME provides four services:
Security Services Security Mechanism
Message origin authentication Digital Signature
Message integrity Digital Signature
Non-repudiation of origin Digital Signature
Message confidentiality Encryption
97
S/MIME CiphersS/MIME Ciphers
◆ Symmetric encryption◆ 3DES 168 bit
◆ DES 56 bit◆ RC2 128, 64 and 40 bit
◆ Public-Key◆ RSA 512 to 1024 bit
S/MIME SignatureS/MIME Signature
Digest
Alice’s PrivateKey
MIMEencodedformat
Mimeformat
Suppose Alice sends a S/MIME signed e-mail to Bob
98
S/MIME EncryptionS/MIME Encryption
RandomSession Key
Suppose Alice sends a S/MIME encrypted e-mail to Bob
Bob’s PublicKey
Encoding
Plaintext
MimeFormat
Ciphertext
MIMEencodedformat
S/MIME dual Key ?S/MIME dual Key ?
◆ Dual Key Pair◆ One key pair for encryption◆ One key pair for signature and non repudiation
◆ CA must support key backup and recovery◆ Key pair for encryption generated on the CA
itself !◆ Draw back:
◆ Not all Email client support Dual Key Pair
99
S/MIMES/MIME
◆ The student will setup an e-mail system using S/MIME. He will use digital signature and encryption. Certificates retrieval done by ldap.
◆ Time: 45 min◆ p.77
SSL: How it works ?SSL: How it works ?
100
SSLSSL
◆ Secure Sockets Layer TCP/IP socket encryption◆ Provides end-to-end protection of
communications sections◆ Confidentiality protection via encryption◆ Integrity protection with MAC’s◆ Usually authenticates server using a digital
signature (option)◆ Can authenticate client (option)
SSL HistorySSL History
◆ SSL v1 designed by Netscape in 1994◆ Netscape internal usage
◆ SSL v2 shipped with Navigator 1.0 and 2.0◆ Microsoft proposed PCT (Private Communications
Technology), which overcame some SSL v2 shortcomings
◆ SSL v3 latest version◆ The progresses of PCT were echoed in SSL v3
◆ TLS v1 developed by IETF
101
SSL ProtocolSSL Protocol
◆ The SSL protocol runs above TCP/IP◆ The SSL protocol runs below higher-level
protocols such as HTTP or IMAP
SSL Ports from IANASSL Ports from IANA
◆ nsiiops 261/tcp # IIOP Name Service over TLS/SSL ◆ https 443/tcp # http protocol over TLS/SSL ◆ smtps 465/tcp # smtp protocol over TLS/SSL (was ssmtp) ◆ nntps 563/tcp # nntp protocol over TLS/SSL (was snntp) ◆ imap4-ssl 585/tcp # IMAP4+SSL (use 993 instead) ◆ sshell 614/tcp # SSLshell◆ ldaps 636/tcp # ldap protocol over TLS/SSL (was sldap) ◆ ftps-data 989/tcp # ftp protocol, data, over TLS/SSL ◆ ftps 990/tcp # ftp protocol, control, over TLS/SSL ◆ telnets 992/tcp # telnet protocol over TLS/SSL ◆ imaps 993/tcp # imap4 protocol over TLS/SSL ◆ ircs 994/tcp # irc protocol over TLS/SSL ◆ pop3s 995/tcp # pop3 protocol over TLS/SSL (was spop3) ◆ msft-gc-ssl 3269/tcp # Microsoft Global Catalog with LDAP
102
SSL CiphersSSL Ciphers
◆ The SSL protocol supports the use of a variety of different cryptographic algorithms or ciphers◆ DES (56)◆ 3DES (168)◆ RC4 (40 or 128)◆ RC2 (40)◆ Fortezza (96)◆ IDEA (128)◆ SHA-1, MD5◆ DSA◆ RSA (Key exchange)
SSL HandshakeSSL Handshake
◆ Negotiate the cipher suite
◆ Establish a shared session key
◆ Authenticate the server (Optional)
◆ Authenticate the client (Optional)
103
SSL HandshakeSSL Handshake
TCP
Hello
GET URL
Client Server
DATA
Client performs TCP handshake with the server at port 443 for HTTPS which is HTTP in SSL
Start Cipher negotiation. Client sends SSL HELLO containing ciphers supported by the client and a random number.
Start pass secret. Server sends it’s CERTIFICATE.
Client and Server exchange CHANGE CIPHER SPEC and FINISH messages.
Begin bulk encrypted data exchange. Client encrypts and sends HTTP GET.
Server decrypts request, encrypts and sends response
Server sends FINISH and closes with TCP handshake
S
Bulk EncryptedHTTP ProtocolSymmetric
A SSL connection consists of an SSL handshake followed by bulk encrypted protocol
SSLHandshakeAsymmetric0.2 - 4 KB
S
443
Cert
The server responds with a HELLO containing the ciphers to use and a random number. Note the server selects the ciphers to be used. RSA, RC4 and MD5 are most common.
Client uses certificate to encrypt the pre-master Secret and sends to Server. Both compute bulk encryption KEYS from secret and random numbers.
Client authenticate serverClient authenticate server
◆ Is today's date within the validity period?
◆ Is the issuing CA a trusted CA?
◆ Does the issuing CA's public-key validate the issuer's digital signature?
◆ Does the domain name in the server's certificate match the domain name of the server itself?
104
Demo: Wrong URL !Demo: Wrong URL !
Server authenticate clientServer authenticate client
◆ Does the client's public-key validate its digital signature ? (challenge)
◆ Is today's date within the validity period?
◆ Is the issuing CA a trusted CA?
◆ Does the issuing CA's public-key validate the issuer's digital signature?
◆ Is the user's certificate listed in a CRL?
105
SSL TunnelingSSL Tunneling
◆ SSL can provide tunneling to transport TCP port over an encrypted channel
◆ Some tunneling software can use client and server authentication using Certificates X.509
◆ Some tunneling programs◆ Webtop (Sun/Netscape)◆ Stunnel◆ bjorb, Jonama◆ SSLProxy◆ Celo Communicationss (SSR)
http://www.openssl.org/related/apps.html
SSL Tunneling modeSSL Tunneling mode
XX
YY
ZZpop3 127.0.0.1 1234pop3 127.0.0.1 1234
Encrypted SSL tunnel Clear text
POP3 serverPOP3 server
DMZ
Corporate Net
106
SSL Hardware acceleratorSSL Hardware accelerator
◆ RSA key exchange is very CPU Intensive◆ 200 Mhz NT box allows about a dozen concurrent SSL
handshakes◆ Use Multiple server◆ Use Hardware encryption (Intel-IPIVOT, Ncipher,
Rainbow, etc.)
SGCSGC
◆ Server Gated Cryptography◆ Allows strong encryption on a server basis◆ Originally available only to “qualified financial
institutions”◆ Requires a special SGC server certificate
from: ◆ Verisign Global-ID◆ Thawte SuperCert◆ GlobalSign HyperSign128
◆ Etc.http://www.modssl.org/related/gid.html
107
SGCSGC
◆ Enables strong encryption for export’s browser◆ Procedure:
◆ Browser is export version: 40 bit cipher only !◆ Browser connect to SGC-enabled server with 40 bits
cipher◆ Server send his SGC-tagged certificate to browser◆ Browser verifies server certificate and detect that is
issued by a CA root certificate which is tagged to enable SGC
◆ Browser enabled 128 bit ciphers and force a SSL/TLS renegotiation with the stronger cipher suite.
TLSTLS
◆ Transport Layer Security◆ IETF standardized evolution of SSL v3
◆ Update Mac layer to HMAC◆ Updated for newer algorithms
◆ Substantially similar to SSL v3◆ Cleanup of SSL v3
◆ Aka SSL v3.1
◆ Standardized by RFC 2246 (Jan 1999)
108
Installing a SSL Web ServerInstalling a SSL Web Server
◆ Create the key-pair: Public and Private-Keys◆ Each server includes programs to generate these
◆ Generate a CSR (Certificate Signing Request)◆ This adds Information about your server and yourself
◆ Send the CSR to a CA (Certificate Authority) and wait for your Certificate◆ For instance Verisign, or a internal CA
◆ Install the Certificate
If you do not hold a Certificate signed by a well k nown CA,your client’s browser will display warning messages that
the Certificate is from and Unknown CA
Demo: unknown certificateDemo: unknown certificate
109
Setup a SSL web serverSetup a SSL web server
◆ The student will setup a SSL web server using Netscape Enterprise Server
◆ Time: 1 hour◆ p.100
Setup a SSL Client AuthenticationSetup a SSL Client Authentication
◆ The student will setup a SSL client authentication to protect the access to Intranet Server
◆ Time: 1 hour ◆ p.121
110
PKCS#11 Smartcard installationPKCS#11 Smartcard installation
◆ The student will connect and install a smartcard on his PC following PKCS#11 standard
◆ Time: 15 min. ◆ p.136
Playing the security officer...Playing the security officer...
◆ The student plays the security officer character
◆ Time: 30 min. ◆ p.138
111
Revocation with client SSL authenticationRevocation with client SSL authentication
◆ The student will revoke himself and interpret the results
◆ Time: 30 min. ◆ p.141
IPSec: How it works ?IPSec: How it works ?
112
IPSecIPSec
Application
Presentation
Session
Transport
DataLink
Physical
Application
Presentation
Session
Transport
Network
DataLink
Physical
Network
S/MIME, PGP
SSL, TLS, SSH
IPSEC
Hardware link encryption
IPSec will integrate PKI at layer 3
Remember!
IPSec introductionIPSec introduction
◆ Stands for IP Security
◆ Provide site-to-site and/or host-to-site encryption and/or authentication
◆ Driven by the IETF
◆ Mandatory for IPv6, optional for IPv4
113
IPSec: two main IPSec: two main ”” BlocksBlocks ””
◆ IPSec deals with two main “blocks”◆ IPSec - Encryption and Authentication
◆ ESP - Encapsulating Security Payload◆ AH - Authentication Header◆ Two modes: Tunnel and transport
◆ IPSec - Key management◆ IKE, Skip, Manual IPSEC
IPSec: ESP and AHIPSec: ESP and AH
◆ The AH (Authentication Header) is a protocol providing authentication only
◆ The ESP (Encapsulation Protocol) is an IPSEC protocol for packet encryption and encapsulation.
◆ Both protocols offer integrity check with authentication
IP PayloadTCP/UDP AHIP PayloadTCP/UDP
IP PayloadTCP/UDP ESPIP PayloadTCP/UDP
IP PayloadTCP/UDP IP PayloadTCP/UDPESP AH
114
IPSecIPSec Tunnel modeTunnel mode
◆ Each datagram is captured by the security gateway, encapsulated inside an IPSEC packet and sent to a remote security gateway, which “decapsulates” it, and sends the original datagram to its original destination
◆ The two security gateways create a ‘tunnel’through which data is passed
◆ The two hosts (and their applications) are unaware of the encapsulation process
IPSec Tunnel modeIPSec Tunnel mode
IP
TCP
Application
UDP
IP
TCP
Application
UDP
IP
AH/ESP
ProtectedData
IP
AH/ESP
ProtectedData
Protected Traffic
HostsIPSec
gateway
115
IPSec Transport modeIPSec Transport mode
◆ In transport mode, the two hosts serve as a security gateway and encrypt their own data
◆ In this case, there is no need for a tunnel, nor for the double IP header
◆ The two hosts are aware of the encapsulation (since they perform it)
Transport modeTransport mode
Protected Traffic IP
TCP
Application
UDP
IP
TCP
Application
UDP
116
Security Associations (SA)Security Associations (SA)
◆ The SA is shared by the two communicating parties - it provides indications on the algorithms, the keys, the lifetimes and other algorithm dependant information
◆ The SPI (Security Parameter Index) is a number and serves as an index to the SA
◆ Each SA has two SPIs: incoming & outgoing
SPI and SA (Basics)SPI and SA (Basics)
SPI: 0x1234567
Encryption (ESP): DES
Authentication (AH): SHA-1
DES Key: 0x1615613651365365326536
SHA-1: 0x32676362736347672672644
SPI:0x1234567
SA
117
IPSec Key managementIPSec Key management
◆ In order to create the SA, the two parties need to exchange all the security parameters, as well as the keys.
◆ Several methods of key management:◆ Manual keying or manual IPSec (statically defining SPI
and SA). ◆ SKIP (Simple Key Interchange Protocol by SUN
Microsystems)◆ ISAKMP/OAKLEY or IKE: automatic key management
using DH◆ Photuris alternative to IKE using DH
Practically IKE and manualIPSec is prevalent
Manual IPSecManual IPSec
◆ On each gateway a specific SA is defined (according S/WAN) for each remote gateway (SPI, Cipher, Keys, Hash etc.)
◆ Drawback:◆ Very heavy management
◆ Static keys: less security
◆ Often used between different IPSec vendors◆ Cisco to Check Point for instance
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Manual IPSecManual IPSec
SA
SPI
SA
SPI
IKE Key managementIKE Key management
◆ IKE is widely used (OSPF, IPSec etc..)◆ SA proposal and negotiation is done using IKE◆ Peers may be authenticated using X.509
certificate◆ Each IPSec gateway holds a X.509 certificate◆ SA negotiation starts after cross authentication
◆ Alternate method for authentication:◆ Authentication is provided by pre-shared secrets◆ Drawback: heavy key management etc.
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IKE Key management using PKIIKE Key management using PKI
SA
SPI
SA
SPI
Negotiation with Automatic
Key Management
X509X509
Hardware implementation...Hardware implementation...
◆ Tamper proof design◆ Full integration of IPSec for high/slow
bandwidth encryption◆ Centralized management◆ Vendors
◆ Radguard, Cisco, Checkpoint, etc.
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Demo IPSEC with SecuRemoteDemo IPSEC with SecuRemote
Checkpoint architectureCheckpoint architecture
InternetInternet
ISP ISP
Corporate
Network
CertificateAuthority
VPN-1 SecuRemote
client
LDAP-based Directory Server
X.509Certificates
CRL
VPN-1 / FireWall-1
Account Management GUI
VPN-1 / FireWall-1
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Creation of the CA CertificateCreation of the CA Certificate
•Create CA server object in VPN-1 / Firewall-1
•Define where to retrieve CRL’s•Get the CA certificate
Obtain CA certificate from a fileView the CA’s certificateSave it, allow read by another Mgt station
•Create a ldap server for CRL
Creation of Certificate for FirewallCreation of Certificate for Firewall --11
•Define a nickname for the certificate•Generate a PKCS#10 certificate request.•VIEW to display certificate
•Select the text in the window and copy it to the clipboard.
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Creation of Certificate for FirewallCreation of Certificate for Firewall --11
•GET the certificate from the CA
◆ Importing PKCS#12 Certificates◆ Import from a browser◆ Save it as a P12 format
Creation of Certificate for Secure RemoteCreation of Certificate for Secure Remote
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Using Certificates with Using Certificates with SecureRemoteSecureRemote
◆ IKE Authentication.◆ Specify a profile file (.EPF file)
or select a hardware token from the drop-down list.
◆ Enter password for accessing the profile.
Using Certificates with Using Certificates with SecureRemoteSecureRemote
◆ View the certificate by clicking on View Certificate◆ User’s certificate◆ CA’s certificate
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IPSECIPSEC
◆ The student will setup an IPSec link between a client and a GW Checkpoint using X.509 certificates
◆ Time: 1h30◆ p. 155
CEP: How it works ?CEP: How it works ?
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CEPCEP
◆ Certificate Enrollment Protocol (CEP)
◆ A certificate management protocol jointly
developed by Cisco Systems and VeriSign, Inc.
◆ CEP is an early implementation of Certificate
Request Syntax (CRS), a standard proposed to
the Internet Engineering Task Force (IETF).
CEPCEP
◆ CEP specifies how a device communicates
with a CA including:
◆ how to retrieve the CA's public key
◆ how to enroll a device with the CA
◆ how to retrieve a Certificate revocation list (CRL)
◆ CEP uses RSA's PKCS 7 and 10 as key
component technologies
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CEP, cont.CEP, cont.
DEMO: CEPDEMO: CEP
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Cases Studies !Cases Studies !
Encryption references sitesEncryption references sites
◆ SSL
◆ http://www.openssl.org/
◆ http://developer.netscape.com/docs/manuals/security/sslin/
index.htm
◆ http://www.ultranet.com/~fhirsch/Papers/wwwj/article.html
◆ SSH
◆ http://www.ssh.org/
◆ http://www.Datafellows.com/
◆ http://wwwfg.rz.uni-karlsruhe.de/~ig25/ssh-faq/
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Encryption references sitesEncryption references sites
◆ IPSEC
◆ http://web.mit.edu/network/isakmp/
◆ http://www.data.com/tutorials/bullet_online.html
◆ PGP
◆ http://www.pgp.com
◆ http://web.mit.edu/network/pgp.html
◆ S/MIME
◆ http://www.rsasecurity.com/standards/smime
Encryption references sitesEncryption references sites
◆ Miscellaneous
◆ Crypto-Gram :
◆ http://www.counterpane.com/crypto-gram.html
◆ CryptoBytes :
◆ http://www.rsasecurity.com/rsalabs/cryptobytes/
◆ Crypto FAQ V.4.0 :
◆ http://www.rsasecurity.com/rsalabs/faq/
◆ http://www.datelec.com/~maret
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Open discussion...Open discussion...