SKEIN(3)               FreeBSD Library Functions Manual               SKEIN(3)

NAME
     SKEIN256_Init, SKEIN256_Update, SKEIN256_Final, SKEIN256_End,
     SKEIN256_File, SKEIN256_FileChunk, SKEIN256_Data, SKEIN512_Init,
     SKEIN512_Update, SKEIN512_Final, SKEIN512_End, SKEIN512_File,
     SKEIN512_FileChunk, SKEIN512_Data, SKEIN1024_Init, SKEIN1024_Update,
     SKEIN1024_Final, SKEIN1024_End, SKEIN1024_File, SKEIN1024_FileChunk,
     SKEIN1024_Data - calculate the ``SKEIN'' family of message digests

LIBRARY
     Message Digest (MD4, MD5, etc.) Support Library (libmd, -lmd)

SYNOPSIS
     #include <sys/types.h>
     #include <skein.h>

     void
     SKEIN256_Init(SKEIN256_CTX *context);

     void
     SKEIN256_Update(SKEIN256_CTX *context, const unsigned char *data,
         size_t len);

     void
     SKEIN256_Final(unsigned char digest[32], SKEIN256_CTX *context);

     char *
     SKEIN256_End(SKEIN256_CTX *context, char *buf);

     char *
     SKEIN256_File(const char *filename, char *buf);

     char *
     SKEIN256_FileChunk(const char *filename, char *buf, off_t offset,
         off_t length);

     char *
     SKEIN256_Data(const unsigned char *data, unsigned int len, char *buf);

     void
     SKEIN512_Init(SKEIN512_CTX *context);

     void
     SKEIN512_Update(SKEIN512_CTX *context, const unsigned char *data,
         size_t len);

     void
     SKEIN512_Final(unsigned char digest[64], SKEIN512_CTX *context);

     char *
     SKEIN512_End(SKEIN512_CTX *context, char *buf);

     char *
     SKEIN512_File(const char *filename, char *buf);

     char *
     SKEIN512_FileChunk(const char *filename, char *buf, off_t offset,
         off_t length);

     char *
     SKEIN512_Data(const unsigned char *data, unsigned int len, char *buf);

     void
     SKEIN1024_Init(SKEIN1024_CTX *context);

     void
     SKEIN1024_Update(SKEIN1024_CTX *context, const unsigned char *data,
         size_t len);

     void
     SKEIN1024_Final(unsigned char digest[128], SKEIN1024_CTX *context);

     char *
     SKEIN1024_End(SKEIN1024_CTX *context, char *buf);

     char *
     SKEIN1024_File(const char *filename, char *buf);

     char *
     SKEIN1024_FileChunk(const char *filename, char *buf, off_t offset,
         off_t length);

     char *
     SKEIN1024_Data(const unsigned char *data, unsigned int len, char *buf);

DESCRIPTION
     Skein is a new family of cryptographic hash functions based on the
     Threefish large-block cipher.  Its design combines speed, security,
     simplicity, and a great deal of flexibility in a modular package that is
     easy to analyze.  Skein is defined for three different internal state
     sizes--256 bits, 512 bits, and 1024 bits--and any output size.  This
     allows Skein to be a drop-in replacement for the entire SHA family of
     hash functions.

     The SKEIN256_Init(), SKEIN256_Update(), and SKEIN256_Final() functions
     are the core functions.  Allocate an SKEIN256_CTX, initialize it with
     SKEIN256_Init(), run over the data with SKEIN256_Update(), and finally
     extract the result using SKEIN256_Final(), which will also erase the
     SKEIN256_CTX.

     SKEIN256_End() is a wrapper for SKEIN256_Final() which converts the
     return value to a 33-character (including the terminating '\0') ASCII
     string which represents the 256 bits in hexadecimal.

     SKEIN256_File() calculates the digest of a file, and uses SKEIN256_End()
     to return the result.  If the file cannot be opened, a null pointer is
     returned.  SKEIN256_FileChunk() is similar to SKEIN256_File(), but it
     only calculates the digest over a byte-range of the file specified,
     starting at offset and spanning length bytes.  If the length parameter is
     specified as 0, or more than the length of the remaining part of the
     file, SKEIN256_FileChunk() calculates the digest from offset to the end
     of file.  SKEIN256_Data() calculates the digest of a chunk of data in
     memory, and uses SKEIN256_End() to return the result.

     When using SKEIN256_End(), SKEIN256_File(), or SKEIN256_Data(), the buf
     argument can be a null pointer, in which case the returned string is
     allocated with malloc(3) and subsequently must be explicitly deallocated
     using free(3) after use.  If the buf argument is non-null it must point
     to at least 33 characters of buffer space.

     The SKEIN512_ and SKEIN1024_ functions are similar to the SKEIN256_
     functions except they produce a 512-bit, 65 character, or 1024-bit, 129
     character, output.

ERRORS
     The SKEIN256_End() function called with a null buf argument may fail and
     return NULL if:

     [ENOMEM]           Insufficient storage space is available.

     The SKEIN256_File() and SKEIN256_FileChunk() may return NULL when
     underlying open(2), fstat(2), lseek(2), or SKEIN256_End(2) fail.

SEE ALSO
     md4(3), md5(3), ripemd(3), sha(3), sha256(3), sha512(3)

HISTORY
     These functions appeared in FreeBSD 11.0.

AUTHORS
     The core hash routines were imported from version 1.3 of the optimized
     Skein reference implementation written by Doug Whiting as submitted to
     the NSA SHA-3 contest.  The algorithms were developed by Niels Ferguson,
     Stefan Lucks, Bruce Schneier, Doug Whiting, Mihir Bellare, Tadayoshi
     Kohno, Jon Callas, and Jesse Walker.

FreeBSD 13.1-RELEASE-p6          May 21, 2019          FreeBSD 13.1-RELEASE-p6