rmail-encode-string

rmail-encode-string is a compiled Lisp function in `rmail.el'.

(rmail-encode-string STRING MASK)

Encode STRING with integer MASK, by taking the exclusive OR of the
lowest byte in the mask with the first character of string, the
second-lowest-byte with the second character of the string, etc.,
restarting at the lowest byte of the mask whenever it runs out.
Returns the encoded string. Calling the function again with an
encoded string (and the same mask) will decode the string.