In cryptography, CDMF (Commercial Data Masking Facility) is an algorithm developed at IBM in 1992 to reduce the security strength of the 56-bit DES cipher to that of 40-bit encryption, at the time a requirement of U.S. restrictions on export of cryptography.
Rather than a separate cipher from DES, CDMF constitutes a key generation algorithm, called key shortening.
Like DES, CDMF accepts a 64-bit input key, but not all bits are used.
The algorithm consists of the following steps: The resulting 64-bit data is to be used as a DES key.
Due to step 3, a brute force attack needs to test only 240 possible keys.