Insecure TLS_KRB5_EXPORT_WITH_RC2_CBC_40_SHA
- IANA name:
- TLS_KRB5_EXPORT_WITH_RC2_CBC_40_SHA
- Hex code:
- 0x00, 0x27
- TLS Version(s):
- TLS1.0, TLS1.1, TLS1.2, TLS1.3
- Protocol:
- Export-grade Transport Layer Security (TLS EXPORT)
- Key Exchange:
- Kerberos 5 (KRB5)
- Authentication:
- Kerberos 5 (KRB5)
- Encryption:
- Rivest Cipher 2 with 40bit key in Cipher Block Chaining mode (RC2 CBC 40)
- Hash:
- HMAC Secure Hash Algorithm 1 (SHA)
- Included in RFC:
- Machine-readable:
- application/json
Export ciphers used to be legally exportable from the United States of America in the 1990s, when exporting military technology was heavily restricted. Nowadays, they are considered insecure (see freakattack.com).
This key exchange algorithm does not support Perfect Forward Secrecy (PFS) which is recommended, so attackers cannot decrypt the complete communication stream.
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.
There exists a related-key attack found in 1997. With this attack, RC2 can be broken (see schneier.com).
The Secure Hash Algorithm 1 has been proven to be insecure as of 2017 (see shattered.io).