Python PyCrypto: Verify Signature Example.py

def verify_sign(public_key_loc, signature, data):
    '''
    Verifies with a public key from whom the data came that it was indeed 
    signed by their private key
    param: public_key_loc Path to public key
    param: signature String signature to be verified
    return: Boolean. True if the signature is valid; False otherwise. 
    '''
    from Crypto.PublicKey import RSA 
    from Crypto.Signature import PKCS1_v1_5 
    from Crypto.Hash import SHA256 
    from base64 import b64decode 
    pub_key = open(public_key_loc, "r").read() 
    rsakey = RSA.importKey(pub_key) 
    signer = PKCS1_v1_5.new(rsakey) 
    digest = SHA256.new() 
    # Assumes the data is base64 encoded to begin with
    digest.update(b64decode(data)) 
    if signer.verify(digest, b64decode(signature)):
        return True
    return False

Good job, it works.

wonderful

This looks promising, but for some reason I'm getting this error when I try to use it:

... (truncated backtrace) ...
rsakey = RSA.importKey(pub_key)
File "/usr/lib64/python2.7/dist-packages/Crypto/PublicKey/RSA.py", line 665, in importKey
return self._importKeyDER(der)
File "/usr/lib64/python2.7/dist-packages/Crypto/PublicKey/RSA.py", line 588, in _importKeyDER
raise ValueError("RSA key format is not supported")

I get a lot of hits when I search for this error, but the consensus seems to be that python 2.7 with the following libraries should "just work":

from Crypto.PublicKey import RSA
from Crypto.Signature import PKCS1_v1_5
from Crypto.Hash import SHA256
from base64 import b64decode

Does anyone have any helpful suggestions? Thanks in advance!

@peter-wolfenden-zocdoc A wrong passphrase would lead to this error. Please check your passphrase.

nice nice :3 thank, your code help me so much

How can this work for simple client server socket, where a client sends a signed msg and server verifies? How should I send the message and signature both?

@peter-wolfenden-zocdoc You probably did not decoded your string (from base64). Try a rsakey = RSA.importKey(pub_key.decode('base64'))

can anyone show me an example, please? I am not that much frequent in python but want to implement signature validation in an application

does anyone have an idea on how to do this? https://gist.github.com/cevaris/e003cdeac4499d225f06#gistcomment-2369102

Would return signer.verify(digest, b64decode(signature)) work better than the current method?

I get the error
binascii.Error: Incorrect padding
please help!!!!!!

If verification fails, is there a way to get the originally hashed message from the digital signature?