text: /* SPDX-License-Identifier: GPL-2.0 */
  /*
   * Common values and helper functions for the ChaCha and XChaCha stream ciphers.
   *
   * XChaCha extends ChaCha's nonce to 192 bits, while provably retaining ChaCha's
   * security.  Here they share the same key size, tfm context, and setkey
   * function; only their IV size and encrypt/decrypt function differ.
   *
   * The ChaCha paper specifies 20, 12, and 8-round variants.  In general, it is
   * recommended to use the 20-round variant ChaCha20.  However, the other
   * variants can be needed in some performance-sensitive scenarios.  The generic
   * ChaCha code currently allows only the 20 and 12-round variants.
   */
  
  #ifndef _CRYPTO_CHACHA_H
  #define _CRYPTO_CHACHA_H
  
  #include <crypto/skcipher.h>
  #include <linux/types.h>
  #include <linux/crypto.h>
  
  /* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */
  #define CHACHA_IV_SIZE		16
  
  #define CHACHA_KEY_SIZE		32
  #define CHACHA_BLOCK_SIZE	64
  #define CHACHAPOLY_IV_SIZE	12
  
  /* 192-bit nonce, then 64-bit stream position */
  #define XCHACHA_IV_SIZE		32
  
  struct chacha_ctx {
  	u32 key[8];
  	int nrounds;
  };
  
  void chacha_block(u32 *state, u8 *stream, int nrounds);
  static inline void chacha20_block(u32 *state, u8 *stream)
  {
  	chacha_block(state, stream, 20);
  }
  void hchacha_block(const u32 *in, u32 *out, int nrounds);
  
  void crypto_chacha_init(u32 *state, const struct chacha_ctx *ctx, const u8 *iv);
  
  int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
  			   unsigned int keysize);
  int crypto_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
  			   unsigned int keysize);
  
  int crypto_chacha_crypt(struct skcipher_request *req);
  int crypto_xchacha_crypt(struct skcipher_request *req);
  
  #endif /* _CRYPTO_CHACHA_H */
  