Weak TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384
- IANA name:
- TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384
- Hex code:
- 0xC0, 0x2A
- TLS Version(s):
- TLS1.2, TLS1.3
- Protocol:
- Transport Layer Security (TLS)
- Key Exchange:
- Elliptic Curve Diffie-Hellman (ECDH)
- Authentication:
- Rivest Shamir Adleman algorithm (RSA)
- Encryption:
- Advanced Encryption Standard with 256bit key in Cipher Block Chaining mode (AES 256 CBC)
- Hash:
- HMAC Secure Hash Algorithm 384 (SHA384)
- Included in RFC:
- Machine-readable:
- application/json
This key exchange algorithm does not support Perfect Forward Secrecy (PFS) which is recommended, so attackers cannot decrypt the complete communication stream.
There are reports that servers using the RSA authentication algorithm with keys longer than 3072-bit may experience heavy performance issues leading to connection timeouts and even service unavailability if many clients open simultaneous connections.
In 2013, researchers demonstrated a timing attack against several TLS implementations using the CBC encryption algorithm (see isg.rhul.ac.uk). Additionally, the CBC mode is vulnerable to plain-text attacks in TLS 1.0, SSL 3.0 and lower. A fix has been introduced with TLS 1.2 in form of the GCM mode which is not vulnerable to the BEAST attack. GCM should be preferred over CBC.