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TLS-ECDH-RSA-WITH-AES-256-CBC-SHA384 Cipher Suite
A breakdown of the Cipher Suite TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384, its strengths, and its weaknesses.
Key Exchange Mechanism
Elliptic Curve Diffie Hellman - ECDH
Grade - B
Static Elliptic Curve Diffie Hellman (ECDH) does not use ephemeral (temporary) keys, meaning it violates perfect forward secrecy. ECDHE should be used in preference.
Authentication
Rivest, Shamir, Adleman - RSA
Grade - A
RSA as an authentication mechanism in cipher suites is secure because it relies on the difficulty of factoring large prime numbers. This makes it computationally infeasible for attackers to derive the private key from the public key, ensuring confidentiality and integrity in secure communications.
Cipher
Advanced Encryption Standard - AES
Grade - A
AES should be used in cipher suites because it offers strong security with efficient performance, large block size (128 bits), and resistance to known attacks. Its widespread adoption and thorough analysis by the cryptographic community ensure reliability and robustness for encrypting sensitive data.
Hash
Secure Hash Algorithm 384 Bit - SHA384
Grade - A
Improving greatly from SHA1, SHA-256 and above create secure hashes through robust cryptographic algorithms that ensure collision resistance and preimage resistance. They process input data in fixed-size blocks, applying complex mathematical transformations that make it computationally impractical to reverse-engineer the original data from its hash.
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.
