Vulnerabilities in SSL & TLS :- RC4 Byte Biases

Main Points

• The RC4 algorithm has many byte biases (certain bytes are more (or less) likely to appear than others).
• An attacker can use byte biases to recover plaintext bytes at known locations (such as a session token within a cookie) upon encrypting the same plaintext many times and monitoring the ciphertext.
• This attack requires generation of large data volumes.
• It is somewhat impractical but highlights a significant flaw within RC4.

Quick Reference

Description

The RC4 algorithm, which is used in the TLS and SSL protocols, has many single-byte biases, making it easier for remote attackers to carry plaintext-recovery attacks by statistically analysing ciphertext in a large number of sessions that use the same plaintext.

Name

RC4 Byte Biases

CVE Number

CVE-2013-2566

Type of Vulnerability

CBC decryption vulnerability

Affected

Connections supporting RC4

Remediation

Disable support for RC4 algorithm.