MHASH for TCL


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MHTCL

MHTCL is TCL binding to the MHASH library. This file documents version 1.3.0.

This document is copyright © 2002, 2003, 2004 by Marco Maggi.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".


Node:Overview, Next:, Previous:Top, Up:Top

Overview of the library

The MHASH library provides a set of hash algorithms.


Node:TCL API, Next:, Previous:Overview, Up:Top

Accessing the library from TCL

MHTCL creates a single command, [mhash], in the global namespace. To load the package into a TCL interpreter:

package require mhash


Node:Hash Keys, Next:, Up:TCL API

Creating hash keys

mhash hash algorithm Command
Opens a new hashing channel using the selected algorithm. Returns the name of the channel.

The algorithm must be one of: crc32, crc32b, adler32, md5, md4, sha1, sha256, haval256, haval224, haval192, haval160, haval128, ripemd160, tiger, tiger160, tiger128, gost, ripemd128, ripemd256, ripemd320, sha224, sha384, sha512, whirlpool.

See the documentation of MHASH for details about the algorithms.

The hash channel is write-only and we can use with it all the builtin TCL commands for channels: [puts], [close], [fconfigure], [fileevent].

The hash channel supports the special option -digest, which can be used to retrieve the digest of the data processed so far. This option is read-only, it cannot be set. Every time the digest is requested: the internal context of the hash is duplicated and the copy finalised to produce the key. We can request the digest any number of times.

When the channel is closed, the digest is no longer available.

Examples

Generating a hash key for a string of data:

set chan [mhash hash sha1]
puts -nonewline $chan abcdefghilmnopqrstuvz
set key [fconfigure $chan -digest]
close $chan

Generating a hash key for the content of a file:

set thread   [mhash hash md5]
set filename ...
set chan     [open $filename { RDONLY }]
fconfigure $thread -translation binary
fconfigure $chan   -translation binary
fcopy $chan $thread
set key [fconfigure $chan -digest]
close $thread
close $chan


Node:HMAC Keys, Next:, Previous:Hash Keys, Up:TCL API

Creating HMAC keys

mhash hmac algorithm password Command
Opens a new hash channel using the selected algorithm with the HMAC (Hash Message Authentication Codes) method. With this, the produced hash key is associated to a password and cannot be duplicated without it. The method of operation of [mhash hmac] is the same as the one of [mhash hash] (Hash Keys for more informations).

Returns the channel name.

The supported algorithms are a subset of the ones supported by [mhash hash], see [mhash ishmacalgo].


Node:Keygen, Next:, Previous:HMAC Keys, Up:TCL API

Generating keywords

Key generation algorithms allows us to create "random" strings of bytes.

mhash keygen algorithm password length ?option ...? Command
Generate a key of length bytes, using the key generation algorithm, associated with password. Returns the generated key. This is a one-shot command: it doesn't use the channel model of [mhash hash].

The password cannot be an emtpy string; the requested key length can't be zero. algorithm must be one of: mcrypt, asis, hex, pkdes, s2k_simple, s2k_salted, s2k_isalted. See the documentation of MHASH for details about the algorithms.

Supported options:

-hash1 ALGORITHM
a hash algorithm that may be used by the key generation algorithm; defaults to MD5; it is ignored if the key generation algorithm does not require a hash algorithm;
-hash2 ALGORITHM
another hash algorithm that may be used by the key generation algorithm; defaults to SHA1; it is ignored if the key generation algorithm does not require a hash algorithm, or if it requires only one hash algorithm;
-salt DATA
binary data that may be used by the key generation algorithm; defaults to no salt; can be the empty string;
-count INTEGER
if used by the selected key generation algorithm, it's the number of bytes to hash repeatedly (if the password is ten bytes in length and count is twenty, the password is hashed twice); defaults to 0.

Examples

Generating a 10 bytes keyword:

set keyword [mhash keygen mcrypt "passphrase" 10]


Node:Info, Previous:Keygen, Up:TCL API

Getting list of algorithms and the like

mhash info hash exists algorithm Command
Returns true if algorithm is a hash algorithm and is included in this instance of the MHASH library.

mhash info hash list Command
Returns the list of hash algorithms in MHASH.

mhash info hash ishmacalgo algorithm Command
Returns true if the hash algorithm can be used for HMAC.

mhash info hash blocksize algorithm Command
Returns the size of the block used by the hash algorithm; this is the length of the hash key generated by the algorithm.

mhash info keygen exists algorithm Command
Returns true if algorithm is a key generation algorithm and is included in this instance of the MHASH library.

mhash info keygen list Command
Returns the list of key generation algorithms in MHASH.

mhash info keygen usescount algorithm Command
Returns true if the selected key generation algorithm uses the -count option, returns false if it doesn't.

mhash info keygen useshash algorithm Command
Returns the number of hash algorithms used by the selected key generation algorithm. If it is one: we can use the -hash1 option, if it is two: we can use both the -hash1 and -hash2 options.

mhash info keygen usessalt algorithm Command
Returns true if the selected key generation algorithm uses the -salt option, returns false if it doesn't.

mhash info keygen saltsize algorithm Command
Returns the size of the salt used by the key generation algorithm; this value is zero if there's no limit.

mhash info keygen maxkeysize algorithm Command
Returns the maximum size of the key that the selected key generation algorithm may produce; this value is zero if there's no limit.

mhash info version Command
Returns a string representing the MHASH library version number.


Node:C API, Next:, Previous:TCL API, Up:Top

Accessing the library from C

To use the C API of MHTCL, we have to include the header files:

#include <tcl.h>
#include <mhtcl.h>


Node:Data Types, Next:, Up:C API

MHTCL data types

Mhtcl_Thread Opaque Pointer Typedef
The MHTCL structure used to hold MHASH thread data structures.

More_Error Opaque Pointer Typedef
Error descriptor. See tclmore.

More_Block Struct Typedef
Structure representing a block of data. See tclmore.


Node:Symbols, Next:, Previous:Data Types, Up:C API

MHTCL defines

Hash algorithms selectors: MHTCL_HASH_CRC32, MHTCL_HASH_CRC32B, MHTCL_HASH_ADLER32, MHTCL_HASH_MD5, MHTCL_HASH_MD4, MHTCL_HASH_SHA1, MHTCL_HASH_SHA256, MHTCL_HASH_HAVAL256, MHTCL_HASH_HAVAL224, MHTCL_HASH_HAVAL192, MHTCL_HASH_HAVAL160, MHTCL_HASH_HAVAL128, MHTCL_HASH_RIPEMD160, MHTCL_HASH_TIGER, MHTCL_HASH_TIGER160, MHTCL_HASH_TIGER128, MHTCL_HASH_GOST, MHTCL_HASH_RIPEMD128, MHTCL_HASH_RIPEMD256, MHTCL_HASH_RIPEMD320, MHTCL_HASH_SHA224, MHTCL_HASH_SHA384, MHTCL_HASH_SHA512, MHTCL_HASH_WHIRLPOOL.

Key generation algorithms selectors: MHTCL_KEYGEN_MCRYPT, MHTCL_KEYGEN_ASIS, MHTCL_KEYGEN_HEX, MHTCL_KEYGEN_PKDES, MHTCL_KEYGEN_S2K_SIMPLE, MHTCL_KEYGEN_S2K_SALTED, MHTCL_KEYGEN_S2K_ISALTED.


Node:Generating hash, Next:, Previous:Symbols, Up:C API

Generating a hash key

More_Error Mhtcl_OpenHashThread (int algorithm, Mhtcl_Thread *threadVar) Function
Allocates and initialises a new hash thread data structure. algorithm is one of the MHTCL_HASH_* symbols, selecting the algorithm to be used; threadVar is a pointer to a variable that will hold the thread descriptor. Returns NULL or an error descriptor.

void Mhtcl_Digest (Mhtcl_Thread thread, More_Block block) Function
Digests a block of data adding it to the context of a thread.

More_Error Mhtcl_Close (Mhtcl_Thread thread, Tcl_Obj **digest) Function
Ends a thread, freeing all the resources. If digest is not NULL it is the pointer to a variable that will hold the hash key. Return NULL or an error condition.

More_Error Mhtcl_Copy (Mhtcl_Thread source, Mhtcl_Thread * destVar) Function
Duplicates a thread. destVar is a pointer to a variable that will hold the new thread descriptor. Returns NULL or an error descriptor.

More_Error Mhtcl_Abort (Mhtcl_Thread thread) Function
Frees all the resources associated to a thread.


Node:Generating HMAC, Next:, Previous:Generating hash, Up:C API

Generating a HMAC key

int Mhtcl_OpenHMACThread (algorithm, password, threadVar) Function
Allocates and initialises a new HMAC thread.

Arguments:

int algorithm
is a MHTCL_HASH_* symbol representing the hash algorithm to be used;
More_Block password
the password;
Mhtcl_Thread * threadVar
pointer to a variable that will hold the thread descriptor.

Returns NULL or an error descriptor.


Node:Generating keys, Next:, Previous:Generating HMAC, Up:C API

Generating keywords

More_Error Mhtcl_Keygen (algorithm, length, password, hash1, hash2, count, salt, keyVar) Function
Generates a keyword. Arguments:
int algorithm
An integer identifying the key generation algorithm.
int length
The requested length of the key.
More_Block password
The password block.
int hash1
An integer selecting a hash algorithm that may be used by the key generation algorithm.
int hash2
An integer selecting another hash algorithm that may be used by the key generation algorithm.
int count
If used by the selected key generation algorithm, it's the number of bytes to hash repeatedly.
More_Block salt
The salt block: an optional salt that may be used by the key generation algorithm; may be an empty block.
Tcl_Obj ** keyVar
Pointer to the variable that will hold a Byte Array object representing the key.

hash1 and hash2 must be MHTCL_HASH_* symbols.

Returns NULL or an error descriptor.


Node:Hash Channels, Next:, Previous:Generating keys, Up:C API

Associating threads to channels

Tcl_Channel Mhtcl_OpenHashChannel (Mhtcl_Thread thread) Function
Opens a new channel interface to an already existing thread. Returns the channel token.

More_Error Mhtcl_MakeChannelHash (Tcl_Channel channel, Tcl_Obj ** digestVar) Function
Builds the hash digest value from the current state of the channel. digestVar is a pointer to a variable that will hold the digest object.

The hash thread is cloned and terminated: the resulting digest is stored in the selected variable. After the call to this function other data can be added to the channel state, to produce other digests.

Returns NULL or an error descriptor.


Node:Objects, Next:, Previous:Hash Channels, Up:C API

Converting objects to values

int Mhtcl_GetHashAlgFromObj (interp, objPtr, algPtr) Function
Extracts from an object an integer representing a hash algorithm. The object must hold a string from the set of recognised algorithm names.

This function can fail if the string is not an algorithm name.

Arguments:

Tcl_Interp * interp
if not NULL, the interpreter used to report errors;
Tcl_Obj * objPtr
pointer to the source object;
int * algPtr
pointer to a variable that will hold the algorithm identifier (one of the MHTCL_HASH_* symbols.

Returns TCL_OK or TCL_ERROR.

int Mhtcl_GetKeygenAlgFromObj (interp, objPtr, algPtr) Function
Extracts from an object, an integer representing a key generator algorithm. The object must hold a string from the set of recognised algorithm names.

This function can fail if the string is not an algorithm name.

Arguments:

Tcl_Interp * interp
if not NULL, the interpreter used to report errors;
Tcl_Obj * objPtr
the source object;
int * algPtr
pointer to a variable that will hold the algorithm identifier (one of the MHTCL_KEYGEN_* symbols.

Returns TCL_OK or TCL_ERROR.


Node:Miscellaneous functions, Next:, Previous:Objects, Up:C API

Other functions

int Mhtcl_HashExists (int algorithm) Function
Determines if an algorithm is included in the library. algorithm is the algorithm identifier, one of the MHTCL_HASH_* symbols. Returns true if the algorithm is present, else false.

int Mhtcl_IsHMACHash (int algorithm) Function
Determines if a hash algorithm can be used for HMAC. algorithm is the algorithm identifier, one of the MHTCL_HASH_* symbols. Returns true if the algorithm can be used for HMAC, else returns false.

int Mhtcl_HashBlockSize (int algorithm) Function
Accesses the size of the block used by the selected hash algorithm. The value provided by this function is the size of the output digest produced by a hash algorithm.

int Mhtcl_KeygenExists (int algorithm) Function
Determines if an algorithm is included in the library. algorithm is the algorithm identifier, one of the MHTCL_KEYGEN_* symbols. Returns true if the algorithm is present, else false.

int Mhtcl_KeygenUsesSalt (int algorithm) Function
Returns true if the key generation algorithm needs a salt.

int Mhtcl_KeygenSaltSize (int algorithm) Function
Returns the salt size or zero if no limit to the salt size exists.

int Mhtcl_KeygenUsesCount (int algorithm) Function
Returns true if the key generation algorithm makes use of the count argument.

int Mhtcl_KeygenMaxKeySize (int algorithm) Function
Returns the max size or zero if there's no limit to the size for the selected algorithm.

int Mhtcl_KeygenUsesHash (int algorithm) Function
Returns the number of hash algorithms used (max 2) or zero if no hash algorithms are used.

int Mhtcl_MhashVersion (void) Function
Returns a number identifying the MHASH C API version.

Tcl_Obj * Mhtcl_ListHashAlgos (void) Function
Returns a list of strings representing the names of the supported hash algorithms.

Tcl_Obj * Mhtcl_ListKeygenAlgos (void) Function
Returns a list of strings representing the names of the supported key generation algorithms.


Node:Using Stub, Previous:Miscellaneous functions, Up:C API

Using the stub mechanism

The stub mechanism allows us to dynamically link a client extension to a version of MHTCL and to use it with future versions, without recompiling, as long as the future versions do not change the interface.

To do this we link our client extension with the MHTCL's stub library (an object file whose name is something like libmhtclstub...) and compile our code with the symbol USE_MHTCL_STUB defined. Our client library's initialisation function must contain the following code:

#include "mhtcl.h"

...

int
Client_Init (Tcl_Interp *interp)
{
...

#ifdef USE_MHTCL_STUB
  if (Mhtcl_InitStub(interp, "0.5", 0) == NULL)
    {
      return TCL_ERROR;
    }
#endif

...
}

where 0.5 is the version of MHTCL that the client library is supposed to use.

Doing this causes MHTCL include file to declare a preprocessor macro for each function in the interface: the macros are defined like this:

#define Mhtcl_Close     (mhtclStubPtr->mhtcl_Close)

the function calls will be performed through a pointer in a vector of function pointers.


Node:Package License, Next:, Previous:C API, Up:Top

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  11. Each time you redistribute the Library (or any work based on the Library), the recipient automatically receives a license from the original licensor to copy, distribute, link with or modify the Library subject to these terms and conditions. You may not impose any further restrictions on the recipients' exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties with this License.
  12. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Library at all. For example, if a patent license would not permit royalty-free redistribution of the Library by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Library.

    If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply, and the section as a whole is intended to apply in other circumstances.

    It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

    This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.

  13. If the distribution and/or use of the Library is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Library under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.
  14. The Free Software Foundation may publish revised and/or new versions of the Lesser General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

    Each version is given a distinguishing version number. If the Library specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Library does not specify a license version number, you may choose any version ever published by the Free Software Foundation.

  15. If you wish to incorporate parts of the Library into other free programs whose distribution conditions are incompatible with these, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.
  16. BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE LIBRARY, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE LIBRARY "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE LIBRARY IS WITH YOU. SHOULD THE LIBRARY PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
  17. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE LIBRARY AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE LIBRARY (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE LIBRARY TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

How to Apply These Terms to Your New Libraries

If you develop a new library, and you want it to be of the greatest possible use to the public, we recommend making it free software that everyone can redistribute and change. You can do so by permitting redistribution under these terms (or, alternatively, under the terms of the ordinary General Public License).

To apply these terms, attach the following notices to the library. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found.

one line to give the library's name and an idea of what it does.
Copyright (C) year  name of author

This library is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at
your option) any later version.

This library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307,
USA.

Also add information on how to contact you by electronic and paper mail.

You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the library, if necessary. Here is a sample; alter the names:

Yoyodyne, Inc., hereby disclaims all copyright interest in the library
`Frob' (a library for tweaking knobs) written by James Random Hacker.

signature of Ty Coon, 1 April 1990
Ty Coon, President of Vice

That's all there is to it!


Node:Documentation License, Next:, Previous:Package License, Up:Top

GNU Free Documentation License

Version 1.1, March 2000

Copyright © 2000 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA  02111-1307, USA

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

  1. PREAMBLE

    The purpose of this License is to make a manual, textbook, or other written document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

  2. APPLICABILITY AND DEFINITIONS

    This License applies to any manual or other work that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you".

    A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

    A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (For example, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

    The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License.

    The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License.

    A "Transparent" copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, whose contents can be viewed and edited directly and straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup has been designed to thwart or discourage subsequent modification by readers is not Transparent. A copy that is not "Transparent" is called "Opaque".

    Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML designed for human modification. Opaque formats include PostScript, PDF, proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML produced by some word processors for output purposes only.

    The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

  3. VERBATIM COPYING

    You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

    You may also lend copies, under the same conditions stated above, and you may publicly display copies.

  4. COPYING IN QUANTITY

    If you publish printed copies of the Document numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

    If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

    If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a publicly-accessible computer-network location containing a complete Transparent copy of the Document, free of added material, which the general network-using public has access to download anonymously at no charge using public-standard network protocols. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

    It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

  5. MODIFICATIONS

    You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

    1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
    2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has less than five).
    3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
    4. Preserve all the copyright notices of the Document.
    5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
    6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
    7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
    8. Include an unaltered copy of this License.
    9. Preserve the section entitled "History", and its title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
    10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
    11. In any section entitled "Acknowledgments" or "Dedications", preserve the section's title, and preserve in the section all the substance and tone of each of the contributor acknowledgments and/or dedications given therein.
    12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
    13. Delete any section entitled "Endorsements". Such a section may not be included in the Modified Version.
    14. Do not retitle any existing section as "Endorsements" or to conflict in title with any Invariant Section.

    If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

    You may add a section entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties--for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

    You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

    The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

  6. COMBINING DOCUMENTS

    You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice.

    The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

    In the combination, you must combine any sections entitled "History" in the various original documents, forming one section entitled "History"; likewise combine any sections entitled "Acknowledgments", and any sections entitled "Dedications". You must delete all sections entitled "Endorsements."

  7. COLLECTIONS OF DOCUMENTS

    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

    You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

  8. AGGREGATION WITH INDEPENDENT WORKS

    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, does not as a whole count as a Modified Version of the Document, provided no compilation copyright is claimed for the compilation. Such a compilation is called an "aggregate", and this License does not apply to the other self-contained works thus compiled with the Document, on account of their being thus compiled, if they are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one quarter of the entire aggregate, the Document's Cover Texts may be placed on covers that surround only the Document within the aggregate. Otherwise they must appear on covers around the whole aggregate.

  9. TRANSLATION

    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License provided that you also include the original English version of this License. In case of a disagreement between the translation and the original English version of this License, the original English version will prevail.

  10. TERMINATION

    You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

  11. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

  Copyright (C)  year  your name.
  Permission is granted to copy, distribute and/or modify this document
  under the terms of the GNU Free Documentation License, Version 1.1
  or any later version published by the Free Software Foundation;
  with the Invariant Sections being list their titles, with the
  Front-Cover Texts being list, and with the Back-Cover Texts being list.
  A copy of the license is included in the section entitled ``GNU
  Free Documentation License''.

If you have no Invariant Sections, write "with no Invariant Sections" instead of saying which ones are invariant. If you have no Front-Cover Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being list"; likewise for Back-Cover Texts.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.


Node:References, Next:, Previous:Documentation License, Up:Top

References

The authors of MHASH are: Nikos Mavroyanopoulos nmav@hellug.gr and Sascha Schumann sascha@schumann.cx.

The library was originally created by Nikos Mavroyanopoulos sometime in 1998. Many new features and algorithms were added by Sascha Schumann, who maintained it from May 1999 to March 2000. The library is now maintained again by Nikos Mavroyanopoulos.

MHTCL is written by Marco Maggi with no third party code.

The last version of MHTCL can be found here:

<http://web.tiscali.it/marcomaggi/>
<http://gna.org/projects/mhtcl/>
The last version of mhash can be found here:
<http://mhash.sourceforge.net/>
TCL can be found here:
<http://www.tcl.tk/>
The Adler-32 algorithm is defined in RFC 1950.

The MD5 algorithm is defined in RFC 1321.

The MD4 algorithm is defined in RFC 1320.

The S2K (string-to-key) algorithm is described in RFC 2440.

A document about CRC:

<http://www.repairfaq.org/filipg/LINK/F_crc_v3.html>
A page on hash functions:
<http://planeta.terra.com.br/informatica/paulobarreto/hflounge.html>


Node:Concept Index, Previous:References, Up:Top

An entry for each concept

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