Secrets-004: AesGcmEnvelopeCipher.Decrypt now wraps the ArgumentException AesGcm throws for a
wrong-length nonce/tag/wrapped DEK as SecretDecryptionException (as Rewrap already did), so the
resolver's decryption-failed audit fires.
Secrets-007: new MasterKeySnapshot (key + KekId from one reading, zeroed on Dispose) and a
default-implemented IMasterKeyProvider.GetSnapshot(); MasterKeyProviderBase overrides it to
resolve the source once and derive the id from that same key. Encrypt/Decrypt/Rewrap take one
snapshot per KEK and dispose it, so a key file swapped mid-operation can no longer stamp a row
with one key's id and wrap it under another. Intermediate key buffers are zeroed. On-disk format
unchanged: a golden row written by the 0.6.5 cipher still decrypts.
Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV
Joseph Doherty