def decode(cipher, k):
col_length = int(len(cipher)/3)
c = np.array([], dtype=int)
for i in range(len(cipher)):
c = np.append(c, c2i_table(cipher[i]))
c = np.reshape(c,(3,col_length))
plain = np.matmul(u.inv_key(k),c)
plain = np.mod(plain, 31)
p_text = str()
for i in plain.flat:
p_text = p_text+i2c_table(i)
return p_text
def find_key(plain, cipher):
p_col_len = int(len(plain)/3)
c_col_len = int(len(cipher)/3)
p = np.fromstring(plain, dtype=int, sep=' ')
for i in range(len(plain)):
p = np.append(p, c2i_table(plain[i]))
p = np.reshape(p,(3,p_col_len))
c = np.fromstring(cipher, dtype=int, sep=' ')
for i in range(len(cipher)):
c = np.append(c, c2i_table(cipher[i]))
c = np.reshape(c,(3,c_col_len))
key = np.array(np.matmul(c,u.inv_key(p)), dtype=int)
key = np.mod(key, 31)
return key
def get_key(cipher_text, plain_text):
'''
Input:
cipher_text: str
plain_text: str
Return:
key: str
'''
cipher_matrix = convert_text_2_matrix(cipher_text)
plain_matrix = convert_text_2_matrix(plain_text)
key_matrix = np.dot(cipher_matrix, u.inv_key(plain_matrix))
key_matrix = np.mod(key_matrix, 31)
key = ""
for k in key_matrix.flatten():
key += str(k) + " "
return key
def decode_stage(cipher_text, decode_matrix):
'''
Input:
cipher_text: str
decode_matrix: numpy array
Return:
plain_text: str
'''
cipher_matrix = convert_text_2_matrix(cipher_text)
plain_matrix = np.dot(decode_matrix, cipher_matrix)
plain_matrix = np.mod(plain_matrix, 31)
plain_text = convert_matrix_2_text(plain_matrix)
return plain_text
if __name__ == "__main__":
cipher_text = "WPK_FJEIIXZ.OQFPM_"
key = "4 9 -2 3 5 7 1 -6 11"
plain_text_ans = "THI S_I S_A N_A PPL E.."
encode_matrix = np.fromstring(key, dtype=int, sep=" ").reshape(3, 3)
decode_matrix = u.inv_key(encode_matrix)
plain_text = decode_stage(cipher_text, decode_matrix)
print(plain_text)