veyron2/security: Remove PrivateKey accessor from PrivateID interface.
We imagine that private keys are stored in secure storage - like a TPM
or some other simpler factotum service like an ssh-agent. Not keeping
the private keys in memory of the process makes attacks to reveal the
private key significantly harder.
This change modifies the interface so that only a "Sign" method
is exposed. Subsequent changes that introduce the TPM/ssh-agent etc.
will provide identity implementations that do not store the private key
in memory at all but defer to the TPM/agent for signatures.
Change-Id: I1a02694a819177d934590b66854e4ad0253772e0
6 files changed
