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Introduction
The Data
Encryption Standard (DES) algorithm is a block cipher that transforms
64-bit data blocks under a 64-bit secret key, by means of permutation
and substitution. It is officially described in FIPS PUB 46. A new
encryption algorithm, Triple DES was proposed as an alternate to DES.
Overview
DES uses a 56 bit key and maps a 64 bit input block of plaintext onto a
64 bit output block of ciphertext. The basic structure of DES
encryption is as follows: The 64 bit input is first permuted, then
subjected to sixteen rounds, each of which takes the 64 bit output of
the previous round and a 48 bit per-round key and produces a 64 bit
output.The per-round keys are different 48 bit subsets of the 56 bit
key. After the round, the 64 bit output is subjected to the inverse
initial permutation. DES decryption is essentially done by running this
process backwards. A single DES encryption round involves halving the
64 bit input, mangling the right half and the per-round key together
and XOR ing this with the left half, the result is the new right half
while the new left half is simply the old right half. A decryption
round first mangles the left half of the input and the per-round key
together and XOR s this with the right half of the input to produce the
next left half, the new right half being the left half of the input. It
should be noted that the mangling process is not required to be
reversible for the method to work.
Features
- Implementation
based on FIPS46-3
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Supports both encryption and Decryption
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Suitable for Electronic Codebook (ECB), Cipher Block Chaining (CBC),
CFB and OFB implementations
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Fully synchronous design
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High clock speed and low gate count achieved
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Bigendian architecture
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Targetable to Actel and Altera FPGAs
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