Description of the encryption and decryption algorithms
(Note: The algorithms are written in PHP.)
Encryption starts with the generation of a human-readable
key of length seven. This
key is generated by choosing certain letters and digits using
the 'mt_rand' pseudo-random number function. The key
First characters: "acdefhijkmnprtvwxyz"
Subsequent characters: "acdefhijkmnprtvwxyz23479"
A letter is prefixed to the key to indicate which algorithm
version is used.
Next, the input text is padded on the right with DEL (0x7f) characters.
The number of pad characters depends on the key (via the 'md5'
Next, the input text is shuffled depending on the key (via 'md5').
The key mapping used is different from that used for padding.
Next, encryption proper is done. Each character in the input
text is XORed with a number that depends on the key (via 'md5').
The key mapping used is different from that used previously,
and includes dependence on the index in the input text. These
XOR values are converted to human-readable by breaking each 8-bit
value into two 4-bit values, and storing them, using '@' as a
base character offset, in the output text. The resulting
encrypted string characters are '@' and 'A' through 'O'.
Finally, the resulting encrypted string is broken into fixed-length
lines by inserting newline characters. Newlines are ignored by the
Decryption starts with decryption proper, using the same proper
algorithm described above for encryption. Note that if
EncryptedChar = XOR(A,PlaintextChar), then XOR(A,EncryptedChar) is
Next, the input text is shuffled depending on the key, as described
above. The order of shuffling is reversed, so the original order
Finally, the trailing pad characters are removed.
Courtesy of David Spector (www.springtimesoftware.com)