Insecure TLS_KRB5_EXPORT_WITH_DES_CBC_40_MD5
- IANA name:
- TLS_KRB5_EXPORT_WITH_DES_CBC_40_MD5
- Hex code:
- 0x00, 0x29
- 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:
- Data Encryption Standard with 40bit key in Cipher Block Chaining mode (DES CBC 40)
- Hash:
- HMAC Message Digest 5 (MD5)
- 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.
DES is considered weak, primarily due to its short key-lengths of 40 or 65-Bit. Furthermore, it has been withdrawn as a standard by the National Institute of Standards and Technology in 2005.
The Message Digest 5 algorithm suffers form multiple vulnerabilities and is considered insecure.