Exceptions 

class cryptography.exceptions. UnsupportedAlgorithm 

Raised when the requested algorithm, or combination of algorithms is not supported.

class cryptography.exceptions. AlreadyFinalized 

This is raised when a context is used after being finalized.

class cryptography.exceptions. InvalidSignature 

This is raised when signature verification fails. This can occur with HMAC or asymmetric key signature validation.

class cryptography.exceptions. NotYetFinalized 

This is raised when the AEAD tag property is accessed on a context before it is finalized.

class cryptography.exceptions. AlreadyUpdated 

This is raised when additional data is added to a context after update has already been called.

class cryptography.exceptions. InvalidKey 

This is raised when the verify method of a key derivation function’s computed key does not match the expected key.