Unformatted text preview: defense, they planned on using DES until the French government complained; they validated the code with DES but then removed it, and expect people to add it back. I am unimpressed nonetheless. Authentication in SESAME is a function on the first block of a message, not on the entire message. This has the effect of authenticating “Dear Sir” and not the body of a letter. Key generation consists of two calls to the UNIX rand function, which isn’t very random. SESAME uses crc32 and MD5 as one-way hash functions. And of course, SESAME is vulnerable to Kerberos-like password-guessing. 24.8 IBM Common Cryptographic Architecture
The Common Cryptographic Architecture (CCA) was designed and developed by IBM to provide cryptographic primitives for confidentiality, integrity, key management, and personal identification number (PIN) processing [751, 784, 1025, 1026, 940,752]. Keys are managed by control vectors (CVs) (see Section 8.5). Every key has a CV XORed with it and is never separated from the vector unless inside secure hardware. The CV is a data structure providing an intuitive understanding of the privileges associated with a particular key. The individual bits of the CV are defined to have specific meanings for using and handling each key managed by CCA. The CV is carried with the encrypted key in data structures called key tokens. Internal key tokens are used locally and contain keys encrypted under the local master key (MK). External key tokens are used to export and import encrypted keys between systems. Keys in external key tokens are encrypted under key-encrypting keys (KEK). The KEKs are managed in internal key tokens. Keys are separated according to their permitted uses. Key length is also specified and enforced using bits in the CV. Single length keys are 56 bits and are used for such functions as privacy and message authentication. Double length keys are 112 bits and are used for key management, PIN functions, and other special uses. Keys can be required to be DOUBLE-ONLY in which both the left and right halves of the key must be different, DOUBLE in which the halves are permitted to be equal by chance, SINGLE-REPLICATED in which the...
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- Fall '10
- Cryptography, Bruce Schneier, Applied Cryptography, EarthWeb, Search Search Tips