Symmetric ciphers
Rijndael (AES)
Rijndael is the AES winner
and the default cipher used in Filetopia, it is written by Joan
Daemen and Vincent Rijmen. The cipher has a variable block and
key length, and the authors have demonstrated how to extend the
block length and key length by muliples of 32 bits. The design
of Rijndael was influenced by the SQUARE algorithm. The authors
provide a Rijndael specification and a more theoretical paper on
their design
principles. The authors have vowed to never patent Rijndael
RC6
RC6 is Ronald
Rivest's AES submission.
Like all AES ciphers, RC6 works on 128 bit blocks. It
can accept variable length keys. It is very similar
to RC5, incorporating the results of various studies
on RC5 to improve the algorithm. The studies of RC5
found that not all bits of data are used to determine
the rotation amount (rotation is used extensively in
RC5); RC6 uses multiplication to determine the
rotation amount and uses all bits of input data to
determine the rotation amount, strengthening the
avalanche effect.
TwoFish
Twofish is Counterpane Systems' AES submission. Designed by
the Counterpane Team (Bruce Schneier, John Kelsey, Doug Whiting,
David Wagner, Chris Hall, and Niels Ferguson),
Twofish has undergone extensive analysis by the Counterpane Team.
There is a paper available from the Twofish web page and
the source code is provided in optimized C and assembly.
Mars
MARS is IBM's AES submission.
There is a MARS web page,
but it provides little more than a link to the MARS paper. MARS uses
128 bit blocks and supports variable key sizes (from
128 to 1248 bits). MARS is unique in that it combines
virtually every design technique known to
cryptographers in one algorithm. It uses addition and
subtractions, Sboxes, fixed and data dependent
rotations, and multiplications.
Blowfish
Blowfish is a block cipher
designed by Bruce Schneier, author of Applied Cryptography. Blowfish combines a Feistel network, keydependent
SBoxes, and a noninvertible F function to create what is perhaps
one of the most secure algorithms available. There are no known
attacks against Blowfish.
Idea
IDEA,
developed in Zurich, Switzerland by Xuejia Lai and
James Massey, is generally regarded to be the best
and most secure block algorithm available to the
public today. It utilizes a 128bit key and is
designed to be resistant to differential
cryptanalysis. Some attacks have been
made against reduced round IDEA.
Gost
GOST is a
cryptographic algorithm from Russia that appears to
be the Russian analog to DES both politically and
technologically. Its designers took no chances,
iterating the GOST algorithm for 32 rounds and using
a 256 bit key. Although GOST's conservative design
inspires confidence, John Kelsey has discovered a
keyrelation attack on GOST, described in a post to
sci.crypt on 10 February 1996. There are also weak keys in
GOST, but there are too few to be a
problem when GOST is used with its standard set of
Sboxes.
Cast
CAST,
designed by Carlisle Adams and Stafford Taveres, is
shaping up to be a solid algorithm. Its design is
very similar to Blowfish's, with keydependent
SBoxes, a noninvertible f function, and a Feistel
networklike structure (called a
substitutionpermutation network). David Wagner, John
Kelsey, and Bruce
Schneier have discovered a relatedkey attack
on the 64bit version of CAST that requires
approximately 2^{17} chosen plaintexts, one
related query, and 2^{48} offline
computations. The attack
is infeasible at best. CAST is patented by Entrust
Technologies, which has generously released it
for free use. Carlisle
Adams has submitted a version of CAST (CAST256) as an AES candidate.
Misty1
Misty is a
cryptographic algorithm developed by Mitsubishi
Electric after they broke DES in 1994. It is designed
to withstand linear and differential cryptanalysis,
but has not yet been cryptanalysed. As it has not
undergone intensive peer review, the usual caution is
recommended. It is being considered for inclusion
into the SET 2.0 standard.
Table of
Features
Cipher

Patented

MaxKeySize

BlockSize

Speed

RC6 
Yes

2048bits

128bits

1.66mb/s 
TwoFish 
No

256bits

128bits

2.12mb/s 
Mars 
Yes

1248bits

128bits

1.38mb/s 
Rijndael 
No

256bits

128bits

2.12mb/s 
BlowFish 
No

448bits

64bits

2.46mb/s 
Idea 
Yes

128bits

64bits

0.75mb/s 
Gost 
No

256bits

64bits

1.63mb/s 
Cast256 
Yes

256bits

128bits

1.68mb/s 
Cast128 
No

128bits

64bits

2.60mb/s 
Misty1 
Yes

128bits

64bits

1.01mb/s 
Hash
Algorithm
SHA1
SHA1 was
developed by the NSA for NIST as
part of the Secure Hash Standard (SHS). SHA1 is
similar in design to MD4. The original published
algorithm, known as SHA, was modified by NSA to
protect against an unspecified attack; the updated
algorithm is named SHA1. It produces a 160bit digest
 large enough to protect against
"birthday" attacks, where two different
messages are selected to produce the same signature,
for the next decade.
Source Code
The source
code of all the symmetric ciphers and hash component
can be found at the Scramdisk
Delphi site. The author of this implementation is David Barton,
to whom I wish to express my gratitude.