How to encrypt/decrypt using PKCS1_OAEP SHA256

[yohei1126]

Hi,

I have this sample code. As mentioned in this document, Crypto.Hash.SHA1 is used for hash algorithm. How can I use SHA256 instead.
https://pycryptodome.readthedocs.io/en/latest/src/cipher/oaep.html

from Crypto.Cipher import PKCS1_OAEP
from Crypto.PublicKey import RSA

message = b'You can attack now!'
key_public = RSA.importKey(open('rsa_key.pub').read())
key_private = RSA.importKey(open('rsa_key.pem').read())

cipher = PKCS1_OAEP.new(key=key_public)
ciphertext = cipher.encrypt(message)
print(ciphertext)

cipher = PKCS1_OAEP.new(key=key_private)
dec_message = cipher.decrypt(ciphertext)
print(dec_message)

Thanks

[yohei1126]

This does not work

from Crypto.Cipher import PKCS1_OAEP
from Crypto.PublicKey import RSA
from Crypto.Hash import SHA1, SHA256
message = b'You can attack now!'
key_public = RSA.importKey(open('rsa_key.pub').read())
key_private = RSA.importKey(open('rsa_key.pem').read())

cipher = PKCS1_OAEP.new(key=key_public, hashAlgo=SHA256.new()) #, hashAlgo=hash_algo)
ciphertext = cipher.encrypt(message)
print(ciphertext)

cipher = PKCS1_OAEP.new(key=key_private, hashAlgo=SHA256.new()) #, hashAlgo=hash_algo)
dec_message = cipher.decrypt(ciphertext)
print(dec_message)

Got this error

Traceback (most recent call last):
  File "test.py", line 8, in <module>
    cipher = PKCS1_OAEP.new(key=key_public, hashAlgo=SHA256.new()) #, hashAlgo=hash_algo)
  File "/Users/yohei/Downloads/ssh/.venv/lib/python3.7/site-packages/Crypto/Hash/SHA256.py", line 158, in new
    return SHA256Hash().new(data)
  File "/Users/yohei/Downloads/ssh/.venv/lib/python3.7/site-packages/Crypto/Hash/SHA256.py", line 73, in __init__
    result = _raw_sha256_lib.SHA256_init(state.address_of())
  File "/Users/yohei/.pyenv/versions/3.7.11/lib/python3.7/ctypes/__init__.py", line 377, in __getattr__
    func = self.__getitem__(name)
  File "/Users/yohei/.pyenv/versions/3.7.11/lib/python3.7/ctypes/__init__.py", line 382, in __getitem__
    func = self._FuncPtr((name_or_ordinal, self))
AttributeError: dlsym(0x7fe2b5c1ae50, SHA256_init): symbol not found

[yohei1126]

I want to use

• key spec = RSA_2048
• Encryption algorithms RSAES_OAEP_SHA_256

[Legrandin]

The code in your second message should work, but it seems that your pycryptodome installation is not correct.
Can you redo it, and ensure that pycrypto is not installed by mistake (most common cause for such message)?