Linux 5.5 To Finally Kill The Async Block Cipher API In Favor Of SKCIPHER

The crypto code within the Linux kernel for the upcoming 5.5 cycle finishes converting the drivers to making full use of the four-year-old SKCIPHER interface so that the old ABLKCIPHER code can be removed.

SKCIPHER was introduced in 2015 to the mainline kernel to ultimately replace BLKCIPHER/ABLKCIPHER. This "symmetric key cipher" interface is a generic encrypt/decrypt wrapper for ciphers.

With the upcoming Linux 5.5 cycle, many crypto drivers are finally switching to the skcipher API. As those commits explain, "While all consumers of the API have been converted long ago, some producers of the ablkcipher remain, forcing us to keep the ablkcipher support routines alive, along with the matching code to expose [a]blkciphers via the skcipher API. So switch this driver to the skcipher API, allowing us to finally drop the ablkcipher code in the near future."

That "near future" is "now" with Linux 5.5. Following those commits in the crypto development branch, ablkcipher is nuked. The Asynchronous Block Cipher API was deprecated for a while but now removed in full thanks to completing the SKCIPHER transition. This trims more than one thousand lines of code by dropping that deprecated code not to mention the transitioning of the crypto drivers to the SKCIPHER API generally saved a few lines of code in each driver.

The SKCIPHER interface is documented here for those interested.