AES GCM SIV is a [variant](https://en.wikipedia.org/wiki/AES-GCM-SIV) of GCM that tolerates some forms of nonce reuse. AWS-LC [supports](https://github.com/aws/aws-lc/blob/3cf948b864e4e3308a3bdafd2859cb94dd279af4/include/openssl/aead.h#L141-L145) this mode.
