def decode(ciphertext, alphabet, increment, multiplier):
modulo = len(alphabet)
assert gcd(multiplier, modulo) == 1 # multiplier and length have to be co-primes
multiplier_inverse = inverse(multiplier, modulo) # TODO
plaintext = substitute(ciphertext, alphabet, lambda x: multiplier_inverse * (x - increment))
return plaintext
def encode(plaintext, alphabet, increment, multiplier,):
assert gcd(multiplier, len(alphabet)) == 1 # multiplier and length have to be co-primes
ciphertext = substitute(plaintext, alphabet, lambda x: x * multiplier + increment)
return ciphertext
#Kabopan - Readable Algorithms. Public Domain, 2007-2009
from kbp._misc import (
byteswap, char_range, countmissing, gcd, getbinlen, getbinstr, gethexstr,
gethyphenstr, getlongestcommon, getpadbinstr, getunkbinstr,
getvaluefrombinarystring, bin2hex, ASCII, as_words,
hex2bin, insert_string, int2bebin, int2lebin, lcm, md5, modifystring,
nibbleswap, rol, ror, rorstr, setstr, zip_extend, lcm, slice_and_pad)
import struct
assert char_range("A", "Z") == "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
#gcd
#returns the greatest common divisor of both parameters
assert gcd(6, 8) == 2
#lcm
#returns the least common multiplier of both parameters
assert lcm(6, 9) == 18
assert lcm(6, 8) == 24
assert getbinlen(0) == 1
assert getbinlen(1) == 1
assert getbinlen(3) == 2
assert getvaluefrombinarystring("1000") == 8
assert getvaluefrombinarystring("001000") == 8
assert getpadbinstr(8, 8) == "00001000"
def coprimes(x):
return [i for i in xrange(x) if (gcd(i, x) == 1)]
from kbp._misc import (byteswap, char_range, countmissing, gcd, getbinlen,
getbinstr, gethexstr, gethyphenstr, getlongestcommon,
getpadbinstr, getunkbinstr, getvaluefrombinarystring,
bin2hex, ASCII, as_words, hex2bin, insert_string,
int2bebin, int2lebin, lcm, md5, modifystring,
nibbleswap, rol, ror, rorstr, setstr, zip_extend, lcm,
slice_and_pad)
import struct
assert char_range("A", "Z") == "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
#gcd
#returns the greatest common divisor of both parameters
assert gcd(6, 8) == 2
#lcm
#returns the least common multiplier of both parameters
assert lcm(6, 9) == 18
assert lcm(6, 8) == 24
assert getbinlen(0) == 1
assert getbinlen(1) == 1
assert getbinlen(3) == 2
assert getvaluefrombinarystring("1000") == 8
assert getvaluefrombinarystring("001000") == 8
assert getpadbinstr(8, 8) == "00001000"