How to validate a private key using a public key in python

Question

I was wondering how I use a public key to validate a private key.

I have absolute no idea what I am doing

I am given a public key in the form:

" <RSAKeyValue><Modulus>tuRctbsnB4OSsR7gqNy1ovYZ4vDTn543o4ldX8Wthfjk7dAQKPHQYUmB7EyC4qFQ2GY3/Q+mDjJBDCWbsb8gyFuyU3L93UJ/7szvO+2A/t520srjCN4Yv7HirgpAI0LaWlo1UUUixMU2+kYNv/kBeVUL47TvOIpm0JqstQVDHhJtNMwcbY+3Q0nN4D1jNkSrQitCF3Sdms1kwsIFcdHcUh3WcUBkIefcB97DZKVY915IFbhf1/xdpPBa/E0WjNgtF5q4FI5ClH2CxsDwy2mL6qzZMvRPNWUhaFKlX+CcGvFQOtuJ4K8PZ0P3Wsq55ccxafZp3BQrEcBbto5Cll/E0Q==</Modulus><Exponent>AQAB</Exponent></RSAKeyValue> "

which is a string and I am trying to validate a private key (which is also provided as a string) with it using python. I know what the issuer and audience needs to be but I'm not sure what to do with all this information.

I have looked at some peoples examples of using various packages but I can't seem to figure out what type pub_key, private_key, and message would be... Please help me... I wish to learn

Answer 1

Base 64 decode the components - modulus and public exponent - of the public key from within the XML and create the public key from the decoded unsigned, big endian number values.

Then create a signature with the private key over any data and verify it with the public key using the same RSA signature algorithm such as RSA with PKCS#1 v1.5 padding. If it verifies, the keys form a key pair.