Add DSA interfaces
Change public_key from abstractproperty to abstractmethod
Change public_key from abstractproperty to abstractmethod
fix pep8 errors
Change property names to be consistent with RSA
Change property names to be consistent with RSA
Remove bitlength related properties that are not needed
Changed docstrings to conform to lastest updates of the interfaces
Fixed typo
Change pub_key and priv_key to y and x respectively
Add interfaces changes
Merge branch 'master' into dsa
Apply changes to the DSA API to conform to the latest interface changes
Apply changes to the backend to conform to the latest naming conventions