- IANA name:
- OpenSSL name:
- GnuTLS name:
- Hex code:
- 0x00, 0x1B
- TLS Version(s):
- TLS1.0, TLS1.1, TLS1.2, TLS1.3
- Transport Layer Security (TLS)
- Key Exchange:
- Diffie-Hellman (DH)
- Anonymous (anon)
- Triple-DES (Encrypt Decrypt Encrypt) in Cipher Block Chaining mode (3DES EDE CBC)
- HMAC Secure Hash Algorithm 1 (SHA)
- Included in RFC:
This key exchange algorithm does not support Perfect Forward Secrecy (PFS) which is recommended, so attackers cannot decrypt the complete communication stream.
The so-called Raccoon Attack affects the specifications of TLS 1.2 and below when using a DH(E) key exchange. According to the researchers, while very hard to exploit, in rare circumstances this timing attack allows attackers to decrypt the connection between users and the server. A fix has been introduced in the TLS 1.3 specification.
Anonymous key exchanges are generally vulnerable to Man in the Middle attacks.
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.
While Triple-DES is still recognized as a secure symmetric-key encryption, a more and more standardizations bodies and projects decide to deprecate this algorithm. Though not broken, it has been proven to suffer from several vulnerabilities in the past (see sweet32.info).
The Secure Hash Algorithm 1 has been proven to be insecure as of 2017 (see shattered.io).