S/MIME 4.0 as described in RFC8551 specifies:

2.2. SignatureAlgorithmIdentifier

Receiving agents:

  • MUST support EdDSA with curve25519 using PureEdDSA mode

Sending agents:

  • MUST support at least one of the following algorithms: ECDSA with curve P-256 and SHA-256, or EdDSA with curve25519 using PureEdDSA mode.

2.3. KeyEncryptionAlgorithmIdentifier

Receiving and sending agents:

  • MUST support ECDH ephemeral-static mode for X25519 using HKDF-256

My question:

How do I create a key and a CSR using OpenSSL to create a S/MIME certificate that will use ed25519/curve25519/EdDSA ideally with SHA-512?

Existing guides mostly show how to create a RSA key and a CSR.

  • Can you please provide more specifics on what exactly you have tried? This seems like a well documented process.
    – Ramhound
    Jul 2, 2020 at 14:28
  • That guide is for RSA keys. But i will add some commands
    – neuhaus
    Jul 3, 2020 at 17:08


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