Looking for some Diffie-Hellman APIs

As an experiment in agentic coding in ObjectScript I'm using VS Code to try and create an implementation of an SFTP server.

SFTP is built on top of SSH, so the first phase involves implementing an SSH server. While working on the KEX part of that the agent (using GPT-5.3-Codex) reported:

1. IRIS has what we already need for signing and hashing: RSASHASign, RSASHAVerify, RSAGetLastError, SHAHash, SHA1Hash, SHA3Hash.
2. It does not list a Diffie-Hellman key exchange or modular exponentiation API in %SYSTEM.Encryption.

It then offered these options:

1. Keep using IRIS APIs for cert/key/sign/hash.
2. Add DH modexp via a supported external path (for example OpenSSL command execution inside the container) so we can compute f and K correctly, then sign H with RSASHASign.

I'd prefer to go with #1 so as to avoid calling out to the OS. Does anyone know if the APIs it's looking for exist somewhere inside IRIS?