Insecure TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA
- IANA name:
- TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA
- Hex code:
- 0x00, 0x0B
- TLS Version(s):
- TLS1.0, TLS1.1, TLS1.2, TLS1.3
- Protocol:
- Export-grade Transport Layer Security (TLS EXPORT)
- Key Exchange:
- Diffie-Hellman (DH)
- Authentication:
- Digital Signature Standard (DSS)
- Encryption:
- Data Encryption Standard with 40bit key in Cipher Block Chaining mode (DES40 CBC)
- 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.
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.
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 Furthermore, it has been withdrawn as a standard by the National Institute of Standards and Technology in 2005.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 Secure Hash Algorithm 1 has been proven to be insecure as of 2017 (see shattered.io).