RFC 1829 (rfc1829) - Page 2 of 10
The ESP DES-CBC Transform
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RFC 1829 ESP DES-CBC August 1995 Other implementations exhibit unpredictability, usually through a pseudo-random number generator. Care should be taken that the periodicity of the number generator is long enough to prevent repetition during the lifetime of the session key. 1.3. Data Size The DES algorithm operates on blocks of eight octets. This often requires padding after the end of the unencrypted payload data. Both input and output result in the same number of octets, which facilitates in-place encryption and decryption. On receipt, if the length of the data to be decrypted is not an integral multiple of eight octets, then an error is indicated, as described in [RFC-1825]. 1.4. Performance At the time of writing, at least one hardware implementation can encrypt or decrypt at about 1 Gbps [Schneier94, p. 231]. Karn, Metzger & Simpson Standards Track
