Import a PKCS#8 private key (base64) for SEAL signing. rsa → RSASSA-PKCS1-v1_5 with SHA-256 ecdsa → ECDSA P-256 with SHA-256
Import a PKCS#8 private key (base64) for SEAL signing. rsa → RSASSA-PKCS1-v1_5 with SHA-256 ecdsa → ECDSA P-256 with SHA-256