--- /dev/null
+\input texinfo @c -*-texinfo-*-
+@comment %**start of header
+@setfilename mit-scheme-blowfish.info
+@include version.texi
+@set SCMVERS 9.2.1
+@settitle MIT/GNU Scheme Blowfish Plugin Manual
+@comment %**end of header
+
+@copying
+This manual documents MIT/GNU Scheme Blowfish @value{VERSION}.
+
+Copyright @copyright{} 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014,
+ 2015, 2016, 2017 Matthew Birkholz
+
+@quotation
+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, with no Front-Cover Texts and no Back-Cover Texts.
+A copy of the license is included in the section entitled ``GNU Free
+Documentation License.''
+@end quotation
+@end copying
+
+@dircategory Programming Languages
+@direntry
+* Blowfish: (mit-scheme-blowfish).
+ Blowfish plugin.
+@end direntry
+
+@titlepage
+@title MIT/GNU Scheme Blowfish Plugin Manual
+@subtitle a Blowfish block cipher plugin (version @value{VERSION})
+@subtitle for MIT/GNU Scheme version @value{SCMVERS}
+@subtitle @value{UPDATED}
+@author by Matt Birkholz
+@page
+@vskip 0pt plus 1filll
+@insertcopying
+@end titlepage
+
+@ifnottex
+@node Top
+@top Blowfish Plugin Manual
+
+@insertcopying
+@end ifnottex
+
+@menu
+* Introduction::
+* Procedures::
+* DES Modes::
+* GNU Free Documentation License::
+@end menu
+
+@node Introduction
+@chapter Introduction
+
+This plugin is a dynamically loadable wrapper of the Blowfish block
+cipher C API as implemented by libssl (OpenSSL).
+
+The cipher operates on 64 bit (8 byte) blocks of data and uses a
+variable size key. Keys with 128 bits (16 bytes) are considered good
+for strong encryption. Blowfish can be used in the same modes as DES
+and is currently one of the faster block ciphers. It is quite a bit
+faster than DES, and much faster than IDEA or RC2.
+
+The plugin includes a Scheme procedure to feed bytes from a binary
+input port to the library, and write the encrypted bytes to a binary
+output port.
+
+@node Procedures
+@chapter Procedures
+
+Blowfish consists of a key setup phase and the actual encryption or
+decryption phase.
+
+@deffn Procedure blowfish-set-key bytes
+Generate a Blowfish key from @var{bytes}, which must be 72 bytes or
+less in length. For text keys (strings), apply @code{md5} to the
+string, and use the digest for @var{bytes}.
+@end deffn
+
+@deffn Procedure blowfish-ecb input output key encyrpt?
+Apply Blowfish in Electronic Code Book mode.
+@var{Input} is an 8-byte byte vector.
+@var{Output} is an 8-byte byte vector.
+@var{Key} is a Blowfish key.
+@var{Encrypt?} specifies whether to encrypt (when @code{#t}) or decrypt
+(when @code{#f}).
+@end deffn
+
+The mode functions below all operate on variable length data. They
+all take an initialization vector which needs to be passed along into
+the next call of the same function for the same message. The vector
+may be initialized with anything, but the recipient needs to know what
+it was initialized with, or it won't be able to decrypt. Some
+programs and protocols simplify this, like SSH, where the vector is
+simply initialized to zero. @code{Blowfish-cbc} operates on data that
+is a multiple of 8 bytes long, while @code{blowfish-cfb64} and
+@code{blowfish-ofb64} are used to encrypt any number of bytes. The
+purpose of the latter two is to simulate stream ciphers, and
+therefore, they have a parameter @code{num}, the current offset in the
+initialization vector, which should start at zero and be stored
+between calls.
+
+@deffn Procedure blowfish-cbc input output key init encrypt?
+Apply Blowfish in Cipher Block Chaining mode.
+@var{Input} is a multiple of 8 bytes.
+@var{Output} is the same number of bytes as in Input.
+@var{Key} is a Blowfish key.
+@var{Init} is an 8 byte initialization vector;
+ it is modified after each call.
+ The value from any call may be passed in to a later call.
+@var{Encrypt?} specifies whether to encrypt (when @code{#t}) or decrypt
+(when @code{#f}).
+@end deffn
+
+@deffn Procedure blowfish-cfb64 input istart iend output ostart key init num encrypt?
+Apply Blowfish in Cipher Feed-Back mode.
+@var{Istart} and @var{Iend} specify a range of bytes in @var{Input}.
+@var{Ostart} specifies the first byte to write in @var{Output}.
+@var{Key} is a Blowfish key.
+@var{Init} is an 8 byte initialization vector;
+ it is modified after each call.
+ The value from any call may be passed in to a later call.
+ The initial value must be unique for each message/key pair.
+@var{Num} is an integer from 0 to 7 inclusive, the low 3 bits of the
+ number of bytes that have previously been processed in this stream.
+@var{Encrypt?} specifies whether to encrypt (when @code{#t}) or decrypt
+(when @code{#f}).
+The returned value is the new value of Num.
+@end deffn
+
+@deffn Procedure blowfish-ofb64 input istart iend output ostart key init num
+Apply Blowfish in Output Feed-Back mode.
+@var{Istart} and @var{Iend} specify a range of bytes in @var{Input}.
+@var{Ostart} specifies the first byte to write in @var{Output}.
+@var{Key} is a Blowfish key.
+@var{Init} is an 8 byte initialization vector;
+ it is modified after each call.
+ The value from any call may be passed in to a later call.
+ The initial value must be unique for each message/key pair.
+@var{Num} is an integer from 0 to 7 inclusive, the low 3 bits of the
+ number of bytes that have previously been processed in this stream.
+The returned value is the new value of Num.
+@end deffn
+
+Two convenience procedures are also provided.
+
+@deffn Procedure blowfish-encrypt-port input output key init encrypt?
+Reads bytes from @var{input}, which should be in blocking mode, until
+the end. Feeds the bytes to @code{blowfish-cfb64} and writes the
+resulting, encrypted bytes to @var{output}. @var{Key} and
+@var{init} are passed to @code{blowfish-cfb64} (which modifies
+the latter).
+@var{Encrypt?} specifies whether to encrypt (when @code{#t}) or decrypt
+(when @code{#f}).
+@end deffn
+
+@deffn Procedure compute-blowfish-init-vector
+Returns a new initialization vector that includes a timestamp with a
+resolution of milliseconds, plus 20 random bits. This should make it
+very likely unique.
+@end deffn
+
+The Blowfish cipher was invented and described by Counterpane (see
+@url{http://www.counterpane.com/blowfish.html}). Most of this manual
+was adapted from the OpenSSL manual pages.
+
+@node DES Modes
+@chapter DES Modes
+
+This chapter was written in large parts by Eric Young in his original
+documentation for SSLeay, the predecessor of OpenSSL. In turn, he
+attributed it to:
+
+@smallexample
+AS 2805.5.2
+Australian Standard
+Electronic funds transfer - Requirements for interfaces,
+Part 5.2: Modes of operation for an n-bit block cipher algorithm
+Appendix A
+@end smallexample
+
+@section Electronic Codebook Mode (ECB)
+
+64 bits are enciphered at a time.
+
+The order of the blocks can be rearranged without detection.
+
+The same plain text block always produces the same cipher text block
+(for the same key) making it vulnerable to a dictionary attack.
+
+An error will only affect one cipher text block.
+
+@section Cipher Block Chaining Mode (CBC)
+
+A multiple of 64 bits are enciphered at a time.
+
+The CBC mode produces the same cipher text whenever the same plain text
+is encrypted using the same key and starting variable.
+
+The chaining operation makes the cipher text blocks dependent on the
+current and all preceding plain text blocks and therefore blocks can
+not be rearranged.
+
+The use of different starting variables prevents the same plain text
+enciphering to the same cipher text.
+
+An error will affect the current and the following cipher text blocks.
+
+@section Cipher Feedback Mode (CFB)
+
+Any number of bits, j, up to 64, are enciphered at a time.
+
+The CFB mode produces the same cipher text whenever the same plain text
+is encrypted using the same key and starting variable.
+
+The chaining operation makes the cipher text variables dependent on
+the current and all preceding variables and therefore j-bit variables
+are chained together and can not be rearranged.
+
+The use of different starting variables prevents the same plain text
+enciphering to the same cipher text.
+
+The strength of the CFB mode depends on the size of k (maximal if j
+= k). In my implementation this is always the case.
+
+Selection of a small value for j will require more cycles through the
+encipherment algorithm per unit of plain text and thus cause greater
+processing overheads.
+
+Only multiples of j bits can be enciphered.
+
+An error will affect the current and the following cipher text
+variables.
+
+@section Output Feedback Mode (OFB)
+
+Any number of bits, j, up to 64, are enciphered at a time.
+
+The OFB mode produces the same cipher text whenever the same plain text
+enciphered using the same key and starting variable. More over, in
+the OFB mode the same key stream is produced when the same key and
+start variable are used. Consequently, for security reasons a
+specific start variable should be used only once for a given key.
+
+The absence of chaining makes the OFB more vulnerable to specific
+attacks.
+
+The use of different start variables values prevents the same
+plain text enciphering to the same cipher text, by producing different
+key streams.
+
+Selection of a small value for j will require more cycles through the
+encipherment algorithm per unit of plain text and thus cause greater
+processing overheads.
+
+Only multiples of j bits can be enciphered.
+
+OFB mode of operation does not extend cipher text errors in the
+resultant plain text output. Every bit error in the cipher text causes
+only one bit to be in error in the deciphered plain text.
+
+OFB mode is not self-synchronizing. If the two operations of
+encipherment and decipherment get out of synchronism, the system
+needs to be re-initialized.
+
+Each re-initialization should use a value of the start variable
+different from the start variable values used before with the same
+key. The reason for this is that an identical bit stream would be
+produced each time from the same parameters. This would be
+susceptible to a 'known plain text' attack.
+
+@node GNU Free Documentation License
+@appendix GNU Free Documentation License
+
+@cindex FDL, GNU Free Documentation License
+@center Version 1.2, November 2002
+
+@display
+Copyright @copyright{} 2000,2001,2002 Free Software Foundation, Inc.
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+@end display
+
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+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.
+
+@item
+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
+@uref{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.
+@end enumerate
+
+@page
+@appendixsec 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:
+
+@smallexample
+@group
+ Copyright (C) @var{year} @var{your name}.
+ 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''.
+@end group
+@end smallexample
+
+If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
+replace the ``with...Texts.'' line with this:
+
+@smallexample
+@group
+ with the Invariant Sections being @var{list their titles}, with
+ the Front-Cover Texts being @var{list}, and with the Back-Cover Texts
+ being @var{list}.
+@end group
+@end smallexample
+
+If you have Invariant Sections without Cover Texts, or some other
+combination of the three, merge those two alternatives to suit the
+situation.
+
+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.
+
+@bye
projects / mit-scheme.git / commitdiff