In addition to the deprecation and stripping down of AF_ALG, another piece of the Linux kernel crypto code steaming ahead toward removal is the crypto_rng abstraction layer.

Linux crypto subsystem expert Eric Biggers of Google is working to remove the crypto_rng abstraction layer from the kernel. This generic interface for RNGs is ultimately unnecessary now with it recommended that APIs to the Deterministic Random Bit Generator (DRBG) and Jitterentropy modules are used directly.

Biggers explains in a patch currently pending via the wip-rng Git branch:

"The crypto_rng abstraction layer was designed as a generic interface for random number generators. However, it's now exclusively used to implement a "NIST approved" RNG and the "jitterentropy" entropy collector that supports it (for certification reasons).

Previously some hardware RNG drivers supported crypto_rng. However, that functionality was unused and just caused confusion, as it existed alongside hw_random which is the interface that is actually used.

Reflecting this reality, let's remove the crypto_rng abstraction and make the drbg and jitterentropy modules provide dedicated APIs directly.

To make this work, update the users of crypto_rng accordingly:

- algif_rng.c now calls the DRBG and jitterentropy APIs directly.

- __crypto_stdrng_get_bytes() now calls the DRBG API directly.

- The DRBG self-tests are moved from the testmgr to drbg.c itself, and the DRBG APIs are used directly."

We'll see if this ends up being submitted for the upcoming Linux v7.3 cycle for eliminating the crypto_rng interface.