CHelix v1.07 A
class to implement the "Helix" Encryption and Authentication cipher
CHelix is a C++ implementation for the Helix Encryption and Authentication
algorithm as presented in a November 2003 Dr. Dobb's Journal article by Niels
Ferguson and Bruce Schneier. For further information please refer to the article.
zip file contains the CHelix source
code and also includes a VC 6 workspace file to build a small test app and DLL
version of Helix.
- You are allowed to include the source code in
any product (commercial, shareware, freeware or otherwise) when your product
is released in binary form.
- You are allowed to modify the source code in
any way you want except you cannot modify the copyright details at the top
of each module.
- If you want to distribute source code with
your application, then you are only allowed to distribute versions released
by the author. This is to maintain a single distribution point for the
v1.0 (29 November 2003)
V1.01 (30 November 2003)
- Following an email update from Niels Ferguson, the
following changes were made:
- Removed the need for the doBlk function
- Made the Block function inline.
- Removed the unneeded code "m_i8 >> 31"
- Removed the unneeded local variable tag in the Finish
- Removed the switch statement in preference for a lookup
array in Decrypt.
- plaintext is now not released from Decrypt if the MAC's
do not match up.
- Optimized the key method CHelix::Block by using
register local variables. This now gets the throughput on my machine up to 191
MB / second
V1.02 (1 December 2003)
- Optimized the for loop in Finish. Now it is only called
3 times instead of 4.
V1.03 (1 December 2003)
- Further optimizations as suggested by Serhiy Pavlov
boost the speed to 208 MB / second on my home machine. This corresponds to a
speed of 10.4 clock ticks per byte!,
- Also produced a DLL version of the algorithm, so that
client applications which do not or cannot (e.g. Visual Basic) muck around
with the C++ source code can use the code.
V1.04 (18 June 2004)
- Fixed a bug in the CHelix constructor. Thanks to
Richard Gyger for reporting this problem.
V1.05 (17 September 2004)
- Fixed a number of warnings in the code when compiled in
VC .Net 2003 with the "Force conformance in For Loop Scope" compiler option is
V1.06 (28 October 2004)
- Fixed a problem in the decryption where the
Helix_Decrypt_Masks bit masks were incorrectly defined. Thanks to Dwain
Skinner for reporting and providing a fix for this problem.
- Removed the declaration of #pragma intrinsic(_rotl) as recent Platform SDK's already have this defined.
- Sample app provided with download, now uses console I/O for reporting its results.
V1.07 (30 December 2006)
- Updated copyright details.
- Addition of a CHELIX_EXT_CLASS preprocessor macro to allow the classes
to be more easily added to an extension dll
- Optimized CHelix constructor code.
- Code now uses newer C++ style casts instead of C style casts.
- Updated the code to clean compile on VC2005
- Reworked the layout of the CHelixMAC operator== method
- Replaced use of BOOL with bool in the class.
- Updated documentation to use the same style as the web site
28 December 2016
- Please note that this code is now considered obsolete as it has not been
updated in a long time and from a security point of view AES is now the
recommended cipher to use. For windows wrapper classes for AES encryption
please take a look at the authors CryptoWrappers