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TLS-ECDH-ECDSA-WITH-AES-128-CBC-SHA256 Cipher Suite
A breakdown of the Cipher Suite TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256, 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
Elliptic Curve Digital Signature Algorithm - ECDSA
Grade - A
ECDSA (Elliptic Curve Digital Signature Algorithm) is used in cipher suites for authentication and integrity verification. Its efficiency in generating and verifying digital signatures makes it suitable for secure communication protocols like TLS, ensuring data confidentiality and integrity during exchanges over networks.
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 256 Bit - SHA256
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.
Key Size
128 Bit - 128
Grade - A
128-bit symmetric encryption keys are considered secure because they provide an astronomically large number of possible combinations (2^128), making brute-force attacks computationally infeasible with current technology. This level of security is sufficient for most practical purposes and is widely adopted in various encryption protocols.
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.
