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TLS-DH-anon-WITH-SEED-CBC-SHA Cipher Suite
A breakdown of the Cipher Suite TLS_DH_anon_WITH_SEED_CBC_SHA, its strengths, and its weaknesses.
Key Exchange Mechanism
Diffie Hellman - DH
Grade - B
Static Diffie Hellman (DH) does not use emphemeral (temporary) keys, meaning it violates perfect forward secrecy. Ephemeral Diffie Hellman (EDH) should be used instead.
Cipher
SEED - SEED
Grade - C
Low usage
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.
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.
