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initial commit
2015-09-01 22:53:00 +02:00
## TWENTY4 - a fun stream cipher
*THIS IS JUST FOR LEARINING CRYPTO, DO NOT EVER USE THIS FOR ANYTHING*
This is the implementation of the fun stream cipher TWENTY4 by T.v. Dein, 09/2015.
Published under the public domain, Creative Commons Zero License. It works bytewise,
with keys between 1-256 bits in 17 rounds, uses S-Boxes and key output-feedback mode.
The cipher also works with CBC or ECB mode (sample CBC implementation included).
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The name TWENTY4 is a reference to article 20 paragraph 4 of the german constitution
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which reads:
> All Germans shall have the right to resist any person seeking to
> abolish this constitutional order, if no other remedy is available.
Also, the cipher uses the contents of the german constitution as the source for its
S-Boxes.
## S-Box generation
TWENTY4 uses the german constitution (called "basic law" in germany) as
the source for S-Boxes. The EPUB version (included in sbox/ subdir)
is encrypted using AES-256-CBC with the passphrase
"grundgesetz\n". The resulting byte stream is used as the source for
S-Boxes.
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The following version of the german constitution is used:
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Basic Law for the Federal Republic of Germany in the revised version
published in the Federal Law Gazette Part III, classification number
100-1, as last amended by the Act of 23 December 2014
(Federal Law Gazette I p. 2438).
Linux Shell commands to generate the S-Boxes:
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curl -o BJNR000010949.epub http://www.gesetze-im-internet.de/gg/BJNR000010949.epub
echo grundgesetz > BJNR000010949.pass
cat BJNR000010949.epub | openssl aes-256-cbc -kfile BJNR000010949.pass | ./gen-static-sbox
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'gen-static-sbox' compiled from gen-static-sbox.c in this directory, which has SHA256
checksum: 29bfd8bd6dbca696d4d8b7ca997497e091875d6bf939e9702b1edf669d0742b0.
However, it just prints out bytes which it reads from STDIN, collecting them into an 256
byte array, ignoring possible duplicates, and prints it out as hex.
Both S-Boxes are bijective and have the following properties (calculated using analyze.c):
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Char distribution: 100.000000%
Char redundancy: 0.000000%
Char entropy: 8.000000 bits/char
Compression rate: 0.000000%
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TWENTY4 uses two S-Box arrays, one for key expansion and one for encryption.
## Key expansion
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The input key will be expanded into a 32 byte array. Maximum key size is
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32 bytes (256 bit).
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IV = KU[0]
allow 256 key max
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for ROUND in 0..31
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if KU[ROUND]
K[ROUND] = IV xor KU[ROUND]
else
K[ROUND] = IV yor KBOX[ROUND * 8];
endif
K[ROUND] = KBOX[K[ROUND]]
IV = K[ROUND]
endfor
for KROUND in 0..31
allow 256 key max
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for ROUND in 0..31
fix cipher pseudo code
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K[ROUND] = IV xor (rotateleft(K[ROUND], 3) xor KBOX[rcon(IV)])
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IV = K[ROUND]
endfor
endfor
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where:
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KU: input key
K[17]: initial round key array
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ROUND: encryption round 1-32
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KROUND: key expansion round 1-32
KBOX[256]: pre computed S-Box for key expansion
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## Encryption
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for INBYTE in <INSTREAM>
OUTBYTE = INBYTE
for ROUND in 0..17
OUTBYTE = OUTBYTE xor K[ROUND]
OUTBYTE = OUTBYTE xor SBOX[OUTBYTE]
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OUTBYTE = rotateleft(OUTBYTE, ROUND mod 8)
OUTBYTE = rotateright(K[ROUND], 4)
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endfor
rotatekey(K, OUTBYTE)
OUTBYTE => <OUTSTREAM>
endfor
func rotatekey(K, B)
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PREV = K[31]
for N in 0..31
NEXT = K[N]
K[N] = PREV
fix indent
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PREV = NEXT
K[N] = KBOX[K[N] xor B]
fix typo
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endfor
fix pseudo rotateky() descr
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endfunc
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where:
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K[17]: expanded key
ROUND: encryption round 1-17
INBYTE: one input byte
OUTBYTE: encrypted result for output
SBOX[256]: pre computed S-Box for encryption
fix cipher pseudo code
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rotateleft(B,N): rotate byte B by N bits to the left
rotateright(B,N): rotate byte B by N bits to the right
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## Analysis so far
While this stuff only exists for me to play around with
crypto, I tried to test the cipher a little bit. Here are
my results using a couple of statistical measurements:
I encrypted the GPLv3 contents using the key "1". To compare,
I encrypted the same file with AES-256-CBC using the same
passphrase.
### Check using analyze.c
My own measurement, see analyze.c:
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File size: 35147 bytes
Char distribution: 100.000000%
Char redundancy: 0.000000%
Char entropy: 7.995333 bits/char
Compression rate: 0.000000% (35147 => 35168 bytes)
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For comparision, AES result:
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File size: 35168 bytes
Char distribution: 100.000000%
Char redundancy: 0.000000%
Char entropy: 7.994892 bits/char
Compression rate: 0.000000% (35168 => 35189 bytes)
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## Check using ent
(ent from http://www.fourmilab.ch/random/):
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Entropy = 7.995333 bits per byte.
Optimum compression would reduce the size
of this 35147 byte file by 0 percent.
Chi square distribution for 35147 samples is 229.98, and randomly
would exceed this value 86.79 percent of the times.
Arithmetic mean value of data bytes is 127.6631 (127.5 = random).
Monte Carlo value for Pi is 3.172955438 (error 1.00 percent).
Serial correlation coefficient is -0.004405 (totally uncorrelated = 0.0).
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For comparision, AES result:
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Entropy = 7.994892 bits per byte.
Optimum compression would reduce the size
of this 35168 byte file by 0 percent.
Chi square distribution for 35168 samples is 250.98, and randomly
would exceed this value 55.94 percent of the times.
Arithmetic mean value of data bytes is 127.8717 (127.5 = random).
Monte Carlo value for Pi is 3.151680601 (error 0.32 percent).
Serial correlation coefficient is 0.002014 (totally uncorrelated = 0.0).
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## Check using dieharder
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Checking an nearly infinite output stream, encrypting NULL with 0x01, checked
by dieharder:
% cat /dev/zero | ./twenty4 0x01 e | dieharder -g 200 -a
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#=============================================================================#
# dieharder version 3.31.1 Copyright 2003 Robert G. Brown #
#=============================================================================#
rng_name |rands/second| Seed |
complete
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stdin_input_raw| 6.82e+05 |1515115156|
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#=============================================================================#
test_name |ntup| tsamples |psamples| p-value |Assessment
#=============================================================================#
complete
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diehard_birthdays| 0| 100| 100|0.66702401| PASSED
diehard_operm5| 0| 1000000| 100|0.66534937| PASSED
diehard_rank_32x32| 0| 40000| 100|0.64395558| PASSED
diehard_rank_6x8| 0| 100000| 100|0.73972650| PASSED
diehard_bitstream| 0| 2097152| 100|0.37109308| PASSED
diehard_opso| 0| 2097152| 100|0.61131814| PASSED
diehard_oqso| 0| 2097152| 100|0.78775192| PASSED
diehard_dna| 0| 2097152| 100|0.34538786| PASSED
diehard_count_1s_str| 0| 256000| 100|0.39973600| PASSED
diehard_count_1s_byt| 0| 256000| 100|0.43596185| PASSED
diehard_parking_lot| 0| 12000| 100|0.82562887| PASSED
diehard_2dsphere| 2| 8000| 100|0.89930428| PASSED
diehard_3dsphere| 3| 4000| 100|0.75039182| PASSED
diehard_squeeze| 0| 100000| 100|0.84575916| PASSED
diehard_sums| 0| 100| 100|0.17887215| PASSED
diehard_runs| 0| 100000| 100|0.27394031| PASSED
diehard_runs| 0| 100000| 100|0.38358466| PASSED
diehard_craps| 0| 200000| 100|0.46344932| PASSED
diehard_craps| 0| 200000| 100|0.90279468| PASSED
marsaglia_tsang_gcd| 0| 10000000| 100|0.86230982| PASSED
marsaglia_tsang_gcd| 0| 10000000| 100|0.71786320| PASSED
sts_monobit| 1| 100000| 100|0.95022673| PASSED
sts_runs| 2| 100000| 100|0.97598338| PASSED
sts_serial| 1| 100000| 100|0.91209013| PASSED
sts_serial| 2| 100000| 100|0.76413978| PASSED
sts_serial| 3| 100000| 100|0.47828005| PASSED
sts_serial| 3| 100000| 100|0.89677063| PASSED
sts_serial| 4| 100000| 100|0.99879068| WEAK
sts_serial| 4| 100000| 100|0.93262189| PASSED
sts_serial| 5| 100000| 100|0.97585634| PASSED
sts_serial| 5| 100000| 100|0.50478610| PASSED
sts_serial| 6| 100000| 100|0.08698163| PASSED
sts_serial| 6| 100000| 100|0.03039228| PASSED
sts_serial| 7| 100000| 100|0.62431435| PASSED
sts_serial| 7| 100000| 100|0.74890431| PASSED
sts_serial| 8| 100000| 100|0.87532744| PASSED
sts_serial| 8| 100000| 100|0.91641753| PASSED
sts_serial| 9| 100000| 100|0.11259928| PASSED
sts_serial| 9| 100000| 100|0.04014422| PASSED
sts_serial| 10| 100000| 100|0.18509222| PASSED
sts_serial| 10| 100000| 100|0.91447809| PASSED
sts_serial| 11| 100000| 100|0.51473918| PASSED
sts_serial| 11| 100000| 100|0.38194660| PASSED
sts_serial| 12| 100000| 100|0.08996905| PASSED
sts_serial| 12| 100000| 100|0.72068305| PASSED
sts_serial| 13| 100000| 100|0.06321140| PASSED
sts_serial| 13| 100000| 100|0.83106256| PASSED
sts_serial| 14| 100000| 100|0.08691687| PASSED
sts_serial| 14| 100000| 100|0.36681587| PASSED
sts_serial| 15| 100000| 100|0.10396429| PASSED
sts_serial| 15| 100000| 100|0.10353726| PASSED
sts_serial| 16| 100000| 100|0.98923097| PASSED
sts_serial| 16| 100000| 100|0.58151255| PASSED
rgb_bitdist| 1| 100000| 100|0.83179852| PASSED
rgb_bitdist| 2| 100000| 100|0.13343241| PASSED
rgb_bitdist| 3| 100000| 100|0.64851901| PASSED
rgb_bitdist| 4| 100000| 100|0.27381896| PASSED
rgb_bitdist| 5| 100000| 100|0.53255869| PASSED
rgb_bitdist| 6| 100000| 100|0.23874740| PASSED
rgb_bitdist| 7| 100000| 100|0.24395463| PASSED
rgb_bitdist| 8| 100000| 100|0.32082061| PASSED
rgb_bitdist| 9| 100000| 100|0.23675202| PASSED
rgb_bitdist| 10| 100000| 100|0.14315574| PASSED
rgb_bitdist| 11| 100000| 100|0.49355287| PASSED
rgb_bitdist| 12| 100000| 100|0.94148332| PASSED
rgb_minimum_distance| 2| 10000| 1000|0.90096962| PASSED
rgb_minimum_distance| 3| 10000| 1000|0.40166302| PASSED
rgb_minimum_distance| 4| 10000| 1000|0.39664349| PASSED
rgb_minimum_distance| 5| 10000| 1000|0.33642569| PASSED
rgb_permutations| 2| 100000| 100|0.69292329| PASSED
rgb_permutations| 3| 100000| 100|0.26000392| PASSED
rgb_permutations| 4| 100000| 100|0.98030683| PASSED
rgb_permutations| 5| 100000| 100|0.36223930| PASSED
rgb_lagged_sum| 0| 1000000| 100|0.11113853| PASSED
rgb_lagged_sum| 1| 1000000| 100|0.77935325| PASSED
rgb_lagged_sum| 2| 1000000| 100|0.77721610| PASSED
rgb_lagged_sum| 3| 1000000| 100|0.82307605| PASSED
rgb_lagged_sum| 4| 1000000| 100|0.03644586| PASSED
rgb_lagged_sum| 5| 1000000| 100|0.66058445| PASSED
rgb_lagged_sum| 6| 1000000| 100|0.58785549| PASSED
rgb_lagged_sum| 7| 1000000| 100|0.49955974| PASSED
rgb_lagged_sum| 8| 1000000| 100|0.69106353| PASSED
rgb_lagged_sum| 9| 1000000| 100|0.70361764| PASSED
rgb_lagged_sum| 10| 1000000| 100|0.30173719| PASSED
rgb_lagged_sum| 11| 1000000| 100|0.85554929| PASSED
rgb_lagged_sum| 12| 1000000| 100|0.27246327| PASSED
rgb_lagged_sum| 13| 1000000| 100|0.88260425| PASSED
rgb_lagged_sum| 14| 1000000| 100|0.63519490| PASSED
rgb_lagged_sum| 15| 1000000| 100|0.82192024| PASSED
rgb_lagged_sum| 16| 1000000| 100|0.44669473| PASSED
rgb_lagged_sum| 17| 1000000| 100|0.54589530| PASSED
rgb_lagged_sum| 18| 1000000| 100|0.54788412| PASSED
rgb_lagged_sum| 19| 1000000| 100|0.69862386| PASSED
rgb_lagged_sum| 20| 1000000| 100|0.11040733| PASSED
rgb_lagged_sum| 21| 1000000| 100|0.48511696| PASSED
rgb_lagged_sum| 22| 1000000| 100|0.86570587| PASSED
rgb_lagged_sum| 23| 1000000| 100|0.30541569| PASSED
rgb_lagged_sum| 24| 1000000| 100|0.78320483| PASSED
rgb_lagged_sum| 25| 1000000| 100|0.35409569| PASSED
rgb_lagged_sum| 26| 1000000| 100|0.56956770| PASSED
rgb_lagged_sum| 27| 1000000| 100|0.58603441| PASSED
rgb_lagged_sum| 28| 1000000| 100|0.31877864| PASSED
rgb_lagged_sum| 29| 1000000| 100|0.60119378| PASSED
rgb_lagged_sum| 30| 1000000| 100|0.40966142| PASSED
rgb_lagged_sum| 31| 1000000| 100|0.35013332| PASSED
rgb_lagged_sum| 32| 1000000| 100|0.70995085| PASSED
rgb_kstest_test| 0| 10000| 1000|0.13663827| PASSED
dab_bytedistrib| 0| 51200000| 1|0.50308151| PASSED
dab_dct| 256| 50000| 1|0.50376390| PASSED
Preparing to run test 207. ntuple = 0
dab_filltree| 32| 15000000| 1|0.30158012| PASSED
dab_filltree| 32| 15000000| 1|0.66046482| PASSED
Preparing to run test 208. ntuple = 0
dab_filltree2| 0| 5000000| 1|0.41413034| PASSED
dab_filltree2| 1| 5000000| 1|0.93892964| PASSED
Preparing to run test 209. ntuple = 0
dab_monobit2| 12| 65000000| 1|0.44041006| PASSED
initial commit
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So, all those checks don't look that bad, but of course this doesn't
formatting
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say much about TWENTY4's security. However, not THAT bad for the first cipher :)
initial commit
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