/* SPDX-License-Identifier: GPL-2.0 *//* * AES-CTR and AES-XCTR stream ciphers * * Copyright 2026 Google LLC */#ifndef _CRYPTO_AES_CTR_H#define _CRYPTO_AES_CTR_H #include <crypto/aes.h> /** * aes_ctr() - AES-CTR en/decryption * @dst: The destination buffer.  Can be in-place or out-of-place.  For other *	 overlaps the behavior is unspecified. * @src: The source data * @len: Number of bytes to en/decrypt * @ctr: The counter.  It will be incremented by ceil(@len / AES_BLOCK_SIZE). * @key: The key, already prepared using aes_preparekey() or aes_prepareenckey() * * This implements AES in counter mode with a 128-bit big endian counter. * * This exists only for use by the implementation of modes built on top of CTR * (e.g., GCM and CCM) and some legacy protocols that use CTR mode directly. * Callers are expected to know how to use CTR mode appropriately, including * choosing (key, counter) pairs appropriately to avoid keystream reuse. * * This supports incremental en/decryption.  The length of each non-final chunk * must be a multiple of AES_BLOCK_SIZE, and the updated @ctr must be passed in * each time. * * Context: Any context. */void aes_ctr(u8 *dst, const u8 *src, size_t len,	     u8 ctr[at_least AES_BLOCK_SIZE], aes_encrypt_arg key); /** * aes_xctr() - AES-XCTR en/decryption * @dst: The destination buffer.  Can be in-place or out-of-place.  For other *	 overlaps the behavior is unspecified. * @src: The source data * @len: Number of bytes to en/decrypt * @ctr: The block counter (in host endianness).  For the first call, set it to *	 1.  It will be incremented by ceil(@len / AES_BLOCK_SIZE). * @iv: The initialization vector * @key: The key, already prepared using aes_preparekey() or aes_prepareenckey() * * This implements AES in XOR Counter mode, as specified in the paper * "Length-preserving encryption with HCTR2" * (https://eprint.iacr.org/2021/1441.pdf). * * This exists only for use by the implementation of modes built on top of XCTR. * Callers are expected to know how to use XCTR mode appropriately, including * choosing (key, IV) pairs appropriately to avoid keystream reuse. * * This supports incremental en/decryption.  The length of each non-final chunk * must be a multiple of AES_BLOCK_SIZE, and the updated @ctr must be passed in * each time. * * Context: Any context. */void aes_xctr(u8 *dst, const u8 *src, size_t len, u64 *ctr,	      const u8 iv[at_least AES_BLOCK_SIZE], aes_encrypt_arg key); #endif /* _CRYPTO_AES_CTR_H */