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IDEA(1) DragonFly General Commands Manual IDEA(1)
NAME
idea - encrypt and decrypt using IDEA
SYNOPSIS
idea [ -e | -d ] [ -r ] [ -ecb | -cbcN | -cfbN | -ofbN ]
( -k keyString | -K keyHexString )
[ inputFile [ ouputFile ] ]
idea [ -h | -H ] [ -tan | -abr ]
[ -k keyString | -K keyHexString ]
[ inputFile [ [ ouputFile ] hashvalFile ]
DESCRIPTION
Idea reads inputFile and writes the en/decrypted data to outputFile or
writes the hash value to hashvalFile. If file name is not given in
command line, idea uses standard input or output. If the input file
name is given as '-', idea reads from the standard input.
IDEA (International Data Encryption Algorithm) is a block cipher
developed by Dr. Xuejia Lai and Prof. Dr. J. L. Massey at the Swiss
Federal Institute of Technology.
OPTIONS
-e Encrypt data. (default)
-d Decrypt data.
-r InputFile is a raster-file.
-k Key is specified with keyString.
-K Key and initial values are specified with keyHexString.
-h Compute a 128 bit hash value from the input data. The hash value
is written to hashvalFile (or standard output).
-H Compute a 128 bit hash value from the input data. The input is
copied to outputFile (or standard output) and the hash value is
written to hashvalFile (or standard error).
Notation:
N = interleave factor (1 is default)
z = 128 bit key
x[i] = 64 bit plaintext block
y[i] = 64 bit ciphertext block
x[1]..x[L] = plaintext (last block is filled with zeros)
x[L+1] = length of plaintext in bits
y[1]..y[L+1]= ciphertext
IDEA(z, .) = encryption function
IIDEA(z, .) = decryption function
x = IIDEA(z, IDEA(z ,x))
Encryption / Decrypion Modes:
-ecb electronic code book mode
y[i] = IDEA(z, x[i])
x[i] = IIDEA(z, y[i])
-cbc cipher block chaining mode (cbc1 is default)
y[i] = IDEA(z, x[i] ^ y[i-N])
x[i] = IIDEA(z, y[i]) ^ y[i-N]
-cfb ciphertext feedback mode
y[i] = x[i] ^ IDEA(z, y[i-N])
x[i] = y[i] ^ IDEA(z, y[i-N])
-ofb output feedback mode
h[i] = IDEA(z, h[i-N])
y[i] = x[i] ^ h[i]
x[i] = y[i] ^ h[i]
Hash Functions:
If no key is given, idea uses the all zero key.
hash value = h[L+1] * 2**64 + g[L+1]
h[0] = z / 2**64
g[0] = z % 2**64
-tan tandem DM-scheme (default)
w = IDEA(g[i-1] * 2**64 + x[i], h[i-1])
h[i] = h[i-1] ^ w
g[i] = g[i-1] ^ IDEA(x[i] * 2**64 + w, g[i-1])
-abr abreast DM-scheme
h[i] = h[i-1] ^ IDEA(g[i-1] * 2**64 + x[i], h[i-1])
g[i] = g[i-1] ^ IDEA(x[i] * 2**64 + h[i-1], ~ g[i-1])
Key Formats:
keyHexString = { '0'..'9' | 'a'..'f' | 'A'..'F' | ':' }
keyHexString = z:y[1-N]:y[2-N]:y[3-N]..
keyString = { '!'..'~' } = z
EXAMPLES
To encrypt and decrypt a file in cipher block chaining mode with an
interleave factor of 8:
idea -e -cbc8 -K 12345:67:89::ab:cDEf data data.cr
idea -d -cbc8 -K 12345:67:89::ab:cDef data.cr data.ori
data and data.ori are identical
To compute the hash value with tandem DM-scheme:
idea -h data
To compute the hash value and encrypt the data in one step:
idea -Hk "k e y" data | idea -K 123:9a::eF - data.cr
PATENT
IDEA is registered as the international patent WO 91/18459 "Device for
Converting a Digital Block and the Use thereof". For commercial use of
IDEA, one should contact
ASCOM TECH AG
Freiburgstrasse 370
CH-3018 Bern, Switzerland
AUTHOR
Richard De Moliner (demoliner@isi.ee.ethz.ch)
Signal and Information Processing Laboratory
Swiss Federal Institute of Technology
CH-8092 Zurich, Switzerland
BUGS
This program is at most as strong as IDEA itself. So, we urge the user
to use this program only after he has assured himself that IDEA is
strong enough AND he has read the source code of this program and its
libraries AND he has compiled the program himself with a troyan-free
compiler. WE DO NOT GUARANTEE THAT THIS PROGRAM IS A DECENT ENCRYPTION
PROGRAM.
November 16, 1993 IDEA(1)