RFC 1851 (rfc1851) - Page 3 of 11
The ESP Triple DES Transform
Alternative Format: Original Text Document
RFC 1851 ESP 3DES September 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 3DES 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
Three DES-CBC implementations may be pipelined in series to provide
parallel computation. At the time of writing, at least one hardware
implementation can encrypt or decrypt at about 1 Gbps [Schneier94, p.
231].
Karn, et al Experimental