How to implement a custom RSA-based mechanism

[gilles-peskine-arm]

TF-PSA-Crypto 1.0 and Mbed TLS 4.0 will no longer expose the RSA module, only specific algorithms (PKCS#1 v1.5 encryption, PKCS#1 v1.5 signature, PSS, OAEP). Users who need a diffferent RSA-based mechanism (e.g. full-domain encryption) must contribute an implementation and wait for the next release.

Should TF-PSA-Crypto offer a way to access the private-key and public-key RSA primitives (in Mbed TLS ≤3.x: mbedtls_rsa_public, mbedtls_rsa_private)?

Mailing list thread: https://lists.trustedfirmware.org/archives/list/mbed-tls@lists.trustedfirmware.org/thread/EKDLYVDR6HZPM55HF4ZKNWX7LDEFRCRG/

[gilles-peskine-arm]

Architectural decision: we are not going to provide an API for custom RSA mechanisms in TF-PSA-Crypto 1.0. We may add such a mechanism later based on demand.