How can I verify the signature on my lopy4 device?

[Wenbo]

For example, my signature is got by crypto.generate_rsa_signature.
My code is

self.signature = crypto.generate_rsa_signature(self.computeHash(), key, pers="my_pers")

and then how can I do to verify it?

[Wenbo]

My verify code is

    def isValid(self):
        if self.comefrom == "":
            return True
        global public_sender # public key
        message_decrypted = crypto.rsa_decrypt(self.signature, public_sender)
        return self.computeHash() == message_decrypted

And the function rsa_decrypt can only accept the parameter of a private key. If I use the public key it throws a ValueError:

Traceback (most recent call last):
  File "main.py", line 37, in <module>
  File "/flash/lib/blockChain.py", line 158, in addTransaction
  File "/flash/lib/blockChain.py", line 82, in isValid
ValueError: Invalid private key, mbedtls error code: 0x3D00

So I'm confused ...