hex string's size is being doubled when converted from binary in python3-CodePudding

im encrypting message using rsa when i convert the 256 length cipher text to binary using:

binary_cipher = str(bin(int.from_bytes(cipher_text,byteorder='big'))[2:].zfill(2048))

i get 2048 sized binary string. when i try to convert this binary back to a cipher text using:

encrypted_message = hex(int(binary_cipher,2)).lstrip('0x')

i get a 512 sized cipher text and thus the rsa decryption isnt accepting it because its not the excpected key size (as i understood)

so long story short why my cipher _text's length is getting increased to 512 when i convert it back?

CodePudding user response：

cipher_text = bytes("PREM")

binary_cipher = str(bin(int.from_bytes(cipher_text,byteorder='big'))[2:].zfill(2048))

encrypted_message = hex(int(binary_cipher,2)).lstrip('0x')

print(cipher_text)
print(binary_cipher)
print(encrypted_message)

Here I get "5052454d" which is "PREM" in Hex ASCII.

Working Correctly because Hex is 2 Digits Per ASCII Character.

256 Characters are getting converted to 512 Hex Digits.

To get the ASCII back , try this :

B=bytearray.fromhex(encrypted_message)
B.decode()

Here I get "PREM"