TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA

ECDHE (Elliptic Curve Diffie-Hellman Ephemeral) is used because it enhances security through the use of ephemeral keys, which are temporary and unique for each session. This ensures that even if one session's key is compromised, past and future sessions remain secure. ECDHE provides perfect forward secrecy, meaning that the compromise of long-term keys does not affect the confidentiality of past communications. The ephemeral nature of the keys significantly reduces the risk of long-term data breaches and enhances the overall robustness of the cryptographic protocol.

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.

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 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.