Encryption

Encryption is the conversion of data into a form, called a CIPHER Text.

The use of encryption/decryption is as old as the art of communication.

Encryption/decryption is especially important in wireless communications.

Encryption/decryption is a good idea when carrying out any kind of sensitive transaction.

Ex: A credit-card purchase online, or the discussion of a company secret between

different departments in the organization.

Private key encryption Private key means that each computer has a secret key (code) that it can use to encrypt a packet of information before it is sent over the network to the other computer.

Public Key encryption Public key encryption uses a combination of a private key and a public key.

The key is based on a hash value. This is a value that is computed from a base input number using a hashing algorithm.

Types of Encryption

Encryption depends on modifying or scrambling messages. So a key is necessary to understand the message.If the original message is GOD IS GREATthen the encrypted version depends on the key as follows:

(key = 1) HPE JT HSFBU

(key = 2) IQF KU ITGCV

(key = 3) JRG LV JSHDW

Simple Encryption Example

What is a digital signature? A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document.

A digital signature can be used with any kind of message, whether it is encrypted or not, simply so that the receiver can be sure of the sender's identity and that the message arrived intact.

Digital Signatures

Creation of Digital SignaturesCreation of Digital Signatures

A digital signature scheme typically A digital signature scheme typically consists of three algorithms:consists of three algorithms:

HASHING algorithm.HASHING algorithm. Signature Generation AlgorithmSignature Generation Algorithm A signature verifying algorithm that, given a A signature verifying algorithm that, given a

message, public key and a signature, either message, public key and a signature, either accepts or rejects the message's claim to accepts or rejects the message's claim to authenticity.authenticity.

HashingHashing Hashing is the transformation of a string of characters into Hashing is the transformation of a string of characters into

a usually shorter fixed-length value or key that represents a usually shorter fixed-length value or key that represents the original string.the original string.

As a simple example of the using of hashing in databases, a As a simple example of the using of hashing in databases, a group of people could be arranged in a database like this:group of people could be arranged in a database like this:

Abernathy Sara, Epperdingle Roscoe, Moore Wilfred, Smith David (and many Abernathy Sara, Epperdingle Roscoe, Moore Wilfred, Smith David (and many more sorted into alphabetical order)more sorted into alphabetical order)

After Hashing, each of them will be replaced by a 4 digit After Hashing, each of them will be replaced by a 4 digit number (in this case)number (in this case)

7864=> Abernathy Sara 9802=> Epperdingle Roscoe 1990=> Moore 7864=> Abernathy Sara 9802=> Epperdingle Roscoe 1990=> Moore Wilfred 8822=> Smith David (and so forth). Wilfred 8822=> Smith David (and so forth).

Hashing AlgorithmHashing Algorithm

The formula for hashing depends on two inputs:The formula for hashing depends on two inputs: the sequence of characters representing the the sequence of characters representing the

electronic data to be signedelectronic data to be signed a secret number referred to as a signature's a secret number referred to as a signature's

private key associated with the signing party and private key associated with the signing party and which only that party has access towhich only that party has access to

Some simple Hash FunctionsSome simple Hash Functions The division-remainder methodThe division-remainder method FoldingFolding Radix transformationRadix transformation Digit rearrangementDigit rearrangement

Encryption scrambles or modifies a message or document so it

cannot be read and understood, except by the intended recipient.A key is necessary to reverse the scrambling or modification, to make the message readable.

Methods of Encryption based on Privacy are as follows:

• a message may be digitally signed, but not encrypted• a message may be encrypted first, then digitally signed• a message may be digitally signed first, then encrypted

Methods of Encryption based on PrivacyMethods of Encryption based on Privacy

Public-private digital key pair

Certificate Authority.

The public key certificate creates proof of the identity of the signer by using the services of a certificate authority.

A certificate authority uses a variety of processes to associate the particular public key with an individual.

The combination of public key and proof of identity result in a public key certificate - also called a signer's certificate.

Prerequisites to create a digital signature

It is the process of checking the digital signature by the reference to the original message and a given public key. Verifying also relies on a formula. Here, the formula depends on three inputs:

The sequence of characters representing the supposedly originally signed electronic data The public key of the signing party The value representing the supposedly authentic digital signature.

The output of the formula is a simple answer: YES or NO.

Digital Signature Verification

Digital Signature SchemesDigital Signature Schemes

The following are the widely used The following are the widely used Schemes for Digital SignaturesSchemes for Digital Signatures

RSA SchemeRSA Scheme ElGamal SchemeElGamal Scheme Schnorr Scheme Schnorr Scheme Digital Signature Standard (DSS) Digital Signature Standard (DSS)

Advantages Authentication, identification of the person that signs.

Advantages of Digital Signatures

Integrity of data, every change will be detected.

Non repudiation, because the author cannot be denied of his work (he created and sent).

Imposter preventionElimination of possibility of committing fraud by an imposter

The disadvantages of using digital signatures involve the primary avenue for any business: money.

Though the use of Digital Signatures is very powerful way to secure and authenticate a message or document, its advantages are hampered by lost or theft of keys and the use of vulnerable storage facilities.

A number of Digital Signature standard exist which are incompatible with each other and there is a strong need of a standard through which these different methods (keys) can interact.

Disadvantages