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TLS-KRB5-EXPORT-WITH-RC2-CBC-40-SHA Cipher Suite
A breakdown of the Cipher Suite TLS_KRB5_EXPORT_WITH_RC2_CBC_40_SHA, its strengths, and its weaknesses.
Key Exchange Mechanism
Kerberos 5 - KRB5
Grade - C
Low usage
Cipher
Rivest Cipher 2 - RC2
Grade - D
Deprecated, vulnerable to low cost chosen-prefix attacks. These attacks allow an adversary to generate two different plaintexts that produce the same hash when encrypted. Due to its weak security, RC2 is no longer recommended for use in modern cryptographic applications.< a>.
Hash
Secure Hash Algorithm - SHA
Grade - D
Chosen prefix attacks for SHA1 are feasible at an accessible cost to a well-funded adversary. This level of expense, while significant, does not pose a substantial barrier to attackers with sufficient resources, making such attacks a credible threat.
Key Size
40 Bit - 40
Grade - F
A 40-bit cipher length is too short because it can be easily broken through brute-force attacks due to the limited number of possible keys (2^40). Modern computational power allows attackers to quickly try all potential keys, making 40-bit encryption insufficient for protecting sensitive data.
Cipher Mode
Cipher Block Chaining - CBC
Grade - D
Cipher Block Chaining (CBC) mode is vulnerable to the Lucky13 and POODLE (in TLS v1.2 and below) attacks. The Lucky13 attack exploits timing discrepancies in padding validation, allowing attackers to gradually reveal plaintext. The POODLE attack leverages padding errors to decrypt ciphertext by repeatedly modifying and sending it to the server, observing the error responses. These vulnerabilities arise from CBC’s handling of padding and error messages, making it less secure than modern encryption modes like Galois Counter Mode (GCM), which offer stronger integrity and confidentiality guarantees.
