mathy vanhoefpapers.mathyvanhoef.com/phdthesis-slides.pdf · public phd defense a security analysis...
TRANSCRIPT
Mathy Vanhoef
Public PhD Defense
A Security Analysis of the WPA-TKIP and TLS Security Protocols
Data handled by computers:
2
Banking details Emails Messaging
Adult websites Mobile devicesPrivate files
Goal of dissertation
3
Is the transmission of this data properly protected?
How is data transmitted?
4
Computer
Study security of network protocols used at:
1. Your wireless network
2. Your internet connection
ServerWireless
router
How is data transmitted?
5
Computer
Study security of network protocols used at:
1. Your wireless network
2. Your internet connection
ServerWireless
router
Wireless network security
6
Easy to intercept transmitted data
Computer
Wireless router
Solution: pick password and use encryption!
Available cipher suites?
7
1999 2003 2004
WEP WPA-TKIP AES-CCMP
Available cipher suites?
8
1999 2003 2004
WEP
Broken
WPA-TKIP
Acceptable
AES-CCMP
Secure
Is WPA-TKIP still used?
Usage in 2013:
66% support TKIP
19% support only TKIP
9
Need more arguments to kill TKIP!
Is WPA-TKIP still used?
Usage in 2016:
59% support TKIP
3% support only TKIP
10
Need more arguments to kill TKIP!
Discovered new attacks
11
1. Efficient Denial of Service
2. Forge arbitrary packets to client
3. Decrypt traffic towards client
In 2016, 59% of networks
still are vulnerable!
Impact of attack
12
Computer
Wireless
router
Website
2.2.2.2
Where is detijd.be?
unique address for
every computer
Impact of attack
13
Computer
Wireless
router
Website
2.2.2.2
detijd.be is at 2.2.2.2
unique address for
every computer
Impact of attack
14
Computer
Wireless
router
Website
2.2.2.2
Load detijd.be
Impact of attack
15
Computer
Wireless
router
Attacker
4.4.4.4
Website
2.2.2.2
detijd.be is at 4.4.4.4
Load detijd.be
Impact of attack
16
Computer
Wireless
router
Attacker
4.4.4.4
Website
2.2.2.2
detijd.be is at 4.4.4.4
Victim now contacts
attacker to load detijd.be
Load detijd.be
Conclusion
17
Use only AES-CCMP!
How is data transmitted?
18
Computer
Study security of network protocols used at:
1. Your wireless network
2. Your internet connection
ServerWireless
router
Securing internet traffic
19
Websites can be secured using HTTPS
HTTPS is based on TLS
Internally TLS can use AES, RC4,…
Which one is widely used? Is it secure?
Is RC4 still used?
20
50%
30%
13%
0%
10%
20%
30%
40%
50%
60%
March 2013 Februari 2015 July 2015
In 2013 half of all TLS connections used RC4
RC4 encryption
21
Plaintext
Ciphertext
Keystream
RC4
Key Password123!
RC4
56, 0, 234, 102, 41, …
RC4 encryption
22
Password123! RC4 56, 0, 234, 102, …
The numbers (keystream) should be random
Not the case for RC4 due to biases!
RC4 encryption
23
Password123! RC4 56, 0, 234, 102, …
The numbers (keystream) should be random
Not the case for RC4 due to biases!
≈
Why is this bad?
24
Imagine only second keystream byte is used
≈
When is zero is ‘rolled’, no encryption occurs
Most frequent ciphertextbyte is the real value
25
26
After encryption, image
is unrecognizable
27
?
RC4 biases Most frequent
pixel value is the real value
28
?
Replace all pixels in block
with most frequent value!
29
Try to recover rough outline
using bigger blocks?
30
Try to recover rough outline
using bigger blocks?
31
32
33
Capture multiple encryptions!
Combine with biases to recover all info:
How to recover details?
34
…
…
35
36
37
38
39
Capture multiple encryptions:
Combine with biases to recover all info:
How to recover details?
40
…
…
Summary: abusing RC4 biases
41
EncryptionMultiple
EncryptionsUse Biases
Our contributions
42
We improved these techniques by:
Also using other biases
Generating a list of plaintext candidates
Rapidly generating multiple encryptions
Using this we decrypt a HTTPS cookie.
Cookies are unique identifiers
43
Cookie Identity
ae637f8c5 Mathy
… …
Get newsfeed
Cookie: ae637f8c5
Browser Facebook
Cookies are unique identifiers
44
Cookie Identity
ae637f8c5 Mathy
… …
Get newsfeed
Cookie: ae637f8c5
Return newsfeed of
Mathy Vanhoef
Browser Facebook
Cookies are unique identifiers
45
Cookie Identity
ae637f8c5 Mathy
… …
Get newsfeed
Cookie: ae637f8c5
Return newsfeed of
Mathy Vanhoef
Browser Facebook
Included in
all requests
Decrypting the cookie
46
Browser Facebook Attacker
Cookie:
ae637f8c5
Generate many requests, use biases to recover the cookie!
……
Cookie: …
Cookie: …
Cookie: …
Decrypting 16-character cookie
47
Need one billion encryptions of cookie
Ciphertext copies times 227
Decrypting 16-character cookie
48
Need one billion encryptions of cookie
Takes 75 hours with 4450 requests /
second
Ciphertext copies times 227
Practical impact
49
In response, browsers disabled RC4:
Chrome: dropped support in v48 (20 Jan. 2016)
Firefox: dropped support in v44 (26 Jan. 2016)
IE11: supports RC4
Edge: supports RC4
“will be disabled in forthcoming update”
Decrypting Cookies
50
Questions?