Map of recipientKeyId -> PKCS#8 Base64 private key (supports key rotation).
recipientKeyId
Optional
If true, rejects bundles that do not carry a valid senderSignatureBase64.
senderSignatureBase64
Optional map of senderKeyId -> SPKI Base64 Ed25519 public key for customer sender verification.
senderKeyId
Map of
recipientKeyId-> PKCS#8 Base64 private key (supports key rotation).