SYNOPSIS

package require Tcl 8.2

package require ripemd128 ?1.0.5?

::ripemd::ripemd128 ?-hex? [ -channel channel | -file filename | string ]

::ripemd::hmac128 ?-hex? -key key [ -channel channel | -file filename | string ]

::ripemd::RIPEMD128Init

::ripemd::RIPEMD128Update token data

::ripemd::RIPEMD128Final token

::ripemd::RIPEHMAC128Init key

::ripemd::RIPEHMAC128Update token data

::ripemd::RIPEHMAC128Final token

---

DESCRIPTION

This package is an implementation in Tcl of the RIPEMD-128 message-digest algorithm (1). This algorithm takes an arbitrary quantity of data and generates a 128-bit message digest from the input. The RIPEMD-128 algorithm is based upon the MD4 algorithm (2, 4) but has been cryptographically strengthened against weaknesses that have been found in MD4 (4). RIPEMD-128 has been designed to be a drop-in replacement for MD4 and MD5 (5). If security is the major consideration, then RIPEMD-160 or SHA1 should be considered.

This package will use Trf to accelerate the digest computation if available. In the absence of an accelerator package the pure-Tcl implementation will be used.

COMMANDS

::ripemd::ripemd128 ?-hex? [ -channel channel | -file filename | string ]

Calculate the RIPEMD-128 digest of the data given in string. This is returned as a binary string by default. Giving the -hex option will return a hexadecimal encoded version of the digest.

The data to be hashed can be specified either as a string argument to the ripemd128 command, or as a filename or a pre-opened channel. If the -filename argument is given then the file is opened, the data read and hashed and the file is closed. If the -channel argument is given then data is read from the channel until the end of file. The channel is not closed.

Only one of -file, -channel or string should be given.

::ripemd::hmac128 ?-hex? -key key [ -channel channel | -file filename | string ]

Calculate an Hashed Message Authentication digest (HMAC) using the RIPEMD-128 digest algorithm. HMACs are described in RFC 2104 (6) and provide a RIPEMD-128 digest that includes a key. All options other than -key are as for the ::ripemd::ripemd128 command.

PROGRAMMING INTERFACE

For the programmer, hash functions can be viewed as a bucket into which one pours data. When you have finished, you extract a value that is uniquely derived from the data that was poured into the bucket. The programming interface to the hash operates on a token (equivalent to the bucket). You call RIPEMD128Init to obtain a token and then call RIPEMD128Update as many times as required to add data to the hash. To release any resources and obtain the hash value, you then call RIPEMD128Final. An equivalent set of functions gives you a keyed digest (HMAC).

If you have critcl and have built the tcllibc package then the implementation of the hashing function will be performed by compiled code. Alternatively if both the Trf and Memchan extensions are available then these will be used. Finally the package will revert to a pure-Tcl implementation. The programming interface remains the same, however.

::ripemd::RIPEMD128Init

Begins a new RIPEMD-128 hash. Returns a token ID that must be used for the remaining functions.

::ripemd::RIPEMD128Update token data

Add data to the hash identified by token. Calling RIPEMD128Update $token "abcd" is equivalent to calling RIPEMD128Update $token "ab" followed by RIPEMD128Update $token "cb". See EXAMPLES.

::ripemd::RIPEMD128Final token

Returns the hash value and releases any resources held by this token. Once this command completes the token will be invalid. The result is a binary string of 16 bytes representing the 128 bit RIPEMD-128 digest value.

::ripemd::RIPEHMAC128Init key

This is equivalent to the ::ripemd::RIPEMD128Init command except that it requires the key that will be included in the HMAC.

::ripemd::RIPEHMAC128Update token data

::ripemd::RIPEHMAC128Final token

These commands are identical to the RIPEMD128 equivalent commands.

EXAMPLES

% ripemd::ripemd128 -hex "Tcl does RIPEMD-128"
3cab177bae65205d81e7978f63556c63

% ripemd::hmac128 -hex -key Sekret "Tcl does RIPEMD-128"
b359dc5971a05beea0be7b106b30e389

% set tok [ripemd::RIPEMD128Init]
::ripemd::1
% ripemd::RIPEMD128Update $tok "Tcl "
% ripemd::RIPEMD128Update $tok "does "
% ripemd::RIPEMD128Update $tok "RIPEMD-128"
% ripemd::Hex [ripemd::RIPEMD128Final $tok]
3cab177bae65205d81e7978f63556c63

REFERENCES

[1]

H. Dobbertin, A. Bosselaers, B. Preneel, "RIPEMD-160, a strengthened version of RIPEMD" http://www.esat.kuleuven.ac.be/~cosicart/pdf/AB-9601/AB-9601.pdf

[2]

Rivest, R., "The MD4 Message Digest Algorithm", RFC 1320, MIT, April 1992. (http://www.rfc-editor.org/rfc/rfc1320.txt)

[3]

Rivest, R., "The MD4 message digest algorithm", in A.J. Menezes and S.A. Vanstone, editors, Advances in Cryptology - CRYPTO '90 Proceedings, pages 303-311, Springer-Verlag, 1991.

[4]

Dobbertin, H., "Cryptanalysis of MD4", Journal of Cryptology vol 11 (4), pp. 253-271 (1998)

[5]

Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, MIT and RSA Data Security, Inc, April 1992. (http://www.rfc-editor.org/rfc/rfc1321.txt)

[6]

Krawczyk, H., Bellare, M. and Canetti, R. "HMAC: Keyed-Hashing for Message Authentication", RFC 2104, February 1997. (http://www.rfc-editor.org/rfc/rfc2104.txt)

KEYWORDS

RIPEMD, hashing, md4, message-digest, rfc 1320, rfc 1321, rfc 2104, security

CATEGORY

Hashes, checksums, and encryption

COPYRIGHT

Copyright (c) 2004, Pat Thoyts <[email protected]>