def get_key_from_text(cleartext, cryptedtext):
# Y: crypted text, X: clear text, A: Key
# AX = Y
# A = Y.X^-1
cleartext = cleartext.upper()
cryptedtext = cryptedtext.upper()
clear_array = []
for e in cleartext:
clear_array.append(ord(e)-65)
crypted_array = []
for e in cryptedtext:
crypted_array.append(ord(e)-65)
print crypted_array
matrix_y = [[crypted_array[0], crypted_array[1]], [crypted_array[2], crypted_array[3]]]
found = False
count = 0
while not found:
print "\n\ntry : " + str((count % 4) + 1)
matrix_x = [[clear_array[count + 0], clear_array[count + 1]], [clear_array[count + 2], clear_array[count + 3]]]
print "matrix x"
print matrix_x
print "matrix y"
print matrix_y
import numpy
try:
x_inverse = tools.modMatInv(matrix_x, 27)
print "x inverse"
print x_inverse
y_dot_xinv = numpy.dot(matrix_y, x_inverse)
print "y_dot_xinv = "
print y_dot_xinv
print "K = "
print numpy.mod(y_dot_xinv, 27)
found = True
except ValueError:
count += 4
print " valueError"
def decrypt_text(message, key):
# Pour decrypter il suffit d'inverser la matrice clé
return encrypt_text(message, tools.modMatInv(key, 27))
def decrypt_image(input_filename, output_filename, key):
encrypt_image(input_filename, output_filename, tools.modMatInv(key, 256))