Data cryptography

Encrypting, decrypting and MACing data through a key server session.

Operation	Auth	Purpose
GET /api/v1/crypto/cipher	Bearer + DPoP	The cipher this session currently uses.
POST /api/v1/crypto/cipher	Bearer + DPoP	Select the cipher for this session.
POST /api/v1/crypto/encrypt	Bearer + DPoP	Encrypt data, optionally minting a new key.
POST /api/v1/crypto/decrypt	Bearer + DPoP	Decrypt data.
POST /api/v1/crypto/hmac	Bearer + DPoP	The keyed data hash -- HMAC-SHA384 under a key the key server holds.