TLS_KRB5_EXPORT_WITH_RC2_CBC_40_SHA

Cryptographic algorithms with low adoption should be avoided due to several critical reasons. They often lack rigorous scrutiny and testing by the broader cryptographic community, which increases the risk of undetected vulnerabilities. Moreover, their limited deployment means fewer opportunities for real-world validation and feedback, hindering confidence in their security and interoperability with existing systems. High adoption indicates robustness from extensive scrutiny and successful implementation in diverse environments.

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>.

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.

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 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.