memfrob function reversibly obfuscates an array of binary
data. This is not true encryption; the obfuscated data still bears a
clear relationship to the original, and no secret key is required to
undo the obfuscation. It is analogous to the “Rot13” cipher used on
Usenet for obscuring offensive jokes, spoilers for works of fiction,
and so on, but it can be applied to arbitrary binary data.
Programs that need true encryption—a transformation that completely obscures the original and cannot be reversed without knowledge of a secret key—should use a dedicated cryptography library, such as libgcrypt.
Programs that need to destroy data should use
explicit_bzero (see Erasing Sensitive Data), or possibly
strfry (see Shuffling Bytes).
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
memfrob obfuscates length bytes of data
beginning at mem, in place. Each byte is bitwise xor-ed with
the binary pattern 00101010 (hexadecimal 0x2A). The return value is
memfrob a second time on the same data returns it to
its original state.
Portability Note: This function is unique to the GNU C Library. It is declared in string.h.