Speak Freely for Windows
If a DES key is specified in the Option/Connections... dialogue, it will be
is used to encrypt sound transmitted to that host using a slightly modified
version of the Data Encryption Standard algorithm (the initial and final
permutations, which do not contribute to the security of the algorithm and
exist purely to deter software implementations of DES are not performed). In
order to decrypt sound encoded with DES, the connection on the receiving
machine specify an identical DES key. The DES key phrase can be as long as 255
characters. The actual DES key is created by applying the MD5 algorithm
to the given key phrase, then folding the resulting 128 bit digest into 56 bits
with XOR and AND.
Speak Freely will continue to correctly receive unencrypted sound from a
given host even if a DES key is specified for the connection.