.Dd November 30, 2003
.Dt LIBBLOWFISH 3
.Os NetBSD 1.4T
.Sh NAME
.Nm blowfish_setkey ,
.Nm blowfish_encrypt ,
.Nm blowfish_decrypt
.Nd BLOWFISH encryption/decryption routines
.Sh SYNOPSIS
.Fd #include <blowfish.h>
.br
.Nm cc
.Op Ar arguments
.Fl lblowfish
.br
.Ft void
.Fn blowfish_setkey "BLOWFISH_KEY *key" "const void *key" "int len"
.Ft void
.Fn blowfish_encrypt "const BLOWFISH_KEY *key" "const void *in" "void *out"
.Ft void
.Fn blowfish_decrypt "const BLOWFISH_KEY *key" "const void *in" "void *out"
.Sh DESCRIPTION
These functions perform Blowfish encryption and decryption.
.Pp
.Fn blowfish_setkey
takes a buffer containing a key, which for Blowfish is from 1 to 56
bytes of arbitrary data, performs various computations, and stores the
result into the
.Dv BLOWFISH_KEY
passed in, in an internal format not documented here.  The result is
good for nothing but passing to the other functions.  If the length
passed in is less than 1,
.Fn blowfish_setkey
does nothing; if it is greater than 56, only the first 56 bytes are
used.
.Pp
.Fn blowfish_encrypt
and
.Fn blowfish_decrypt
take a
.Dv BLOWFISH_KEY
and perform encryption or decryption of a block of data.  Blowfish data
blocks are 64 bits, stored as 8 bytes.  The input and output buffers
may overlap arbitrarily without harm.
.Pp
The library promises that the contents of the
.Dv BLOWFISH_KEY
constitute all the state involved; there are no pointers to data
elsewhere.  (For example, sizeof(BLOWFISH_KEY) bytes may be written to
a file and then read back in, in another run, rather than calling
blowfish_setkey, and the result will work perfectly well.)  Another
implication of this is that there is no
.Sq done
call necessary; when finished with a
.Dv BLOWFISH_KEY ,
you can simply drop the memory (deallocate the variable, call
.Xr free 3 ,
whatever).
.Pp
Note that the key structure arguments to
.Fn blowfish_encrypt
and
.Fn blowfish_decrypt
are marked
.Sq const ;
a given
.Dv BLOWFISH_KEY
can be shared my multiple concurrent encryptions and/or decryptions
without any interference therefrom.
.Pp
Corrupting the memory making up a BLOWFISH_KEY will not cause the
library to crash or otherwise violate its interface spec, but using the
resulting key structure with
.Fn blowfish_encrypt
or
.Fn blowfish_decrypt
may produce
.Sq encryption
or
.Sq decryption
that bears no particular resemblance to normal Blowfish operation.
.Sh ERRORS
These routines
.Dq cannot fail ;
the only failure modes possible for them are due to passing invalid pointers
as arguments.  Such incorrect calls will not be detected by the library; their
effects can range from silent corruption of memory to core dumps.
.Sh BUGS
Code blindly assumes 8-bit
.Do
char
.Dc Ns s.
.Sh AUTHOR
der Mouse,
.Aq mouse@rodents.montreal.qc.ca .