FROMGIT: crypto: chacha20-generic - add HChaCha20 library function (bc41a67c) · Commits · e / devices / android_kernel_fairphone_FP3

include/crypto/chacha20.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -17,6 +17,8 @@ struct chacha20_ctx {
		};

		void chacha20_block(u32 state, u8 stream);
		void hchacha20_block(const u32 in, u32 out);

		void crypto_chacha20_init(u32 state, struct chacha20_ctx ctx, u8 *iv);
		int crypto_chacha20_setkey(struct crypto_tfm tfm, const u8 key,
		unsigned int keysize);

lib/chacha20.c

+44 −6

Original line number	Diff line number	Diff line
		/*
		* ChaCha20 256-bit cipher algorithm, RFC7539
		* The "hash function" used as the core of the ChaCha20 stream cipher (RFC7539)
		*
		* Copyright (C) 2015 Martin Willi
		*
		@@ -16,14 +16,10 @@
		#include <asm/unaligned.h>
		#include <crypto/chacha20.h>

		void chacha20_block(u32 state, u8 stream)
		static void chacha20_permute(u32 *x)
		{
		u32 x[16];
		int i;

		for (i = 0; i < ARRAY_SIZE(x); i++)
		x[i] = state[i];

		for (i = 0; i < 20; i += 2) {
		x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 16);
		x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 16);
		@@ -65,6 +61,25 @@ void chacha20_block(u32 state, u8 stream)
		x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7);
		x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 7);
		}
		}

		/**
		* chacha20_block - generate one keystream block and increment block counter
		* @state: input state matrix (16 32-bit words)
		* @stream: output keystream block (64 bytes)
		*
		* This is the ChaCha20 core, a function from 64-byte strings to 64-byte
		* strings. The caller has already converted the endianness of the input. This
		* function also handles incrementing the block counter in the input matrix.
		*/
		void chacha20_block(u32 state, u8 stream)
		{
		u32 x[16];
		int i;

		memcpy(x, state, 64);

		chacha20_permute(x);

		for (i = 0; i < ARRAY_SIZE(x); i++)
		put_unaligned_le32(x[i] + state[i], &stream[i * sizeof(u32)]);
		@@ -72,3 +87,26 @@ void chacha20_block(u32 state, u8 stream)
		state[12]++;
		}
		EXPORT_SYMBOL(chacha20_block);

		/**
		* hchacha20_block - abbreviated ChaCha20 core, for XChaCha20
		* @in: input state matrix (16 32-bit words)
		* @out: output (8 32-bit words)
		*
		* HChaCha20 is the ChaCha equivalent of HSalsa20 and is an intermediate step
		* towards XChaCha20 (see https://cr.yp.to/snuffle/xsalsa-20081128.pdf).
		* HChaCha20 skips the final addition of the initial state, and outputs only
		* certain words of the state. It should not be used for streaming directly.
		*/
		void hchacha20_block(const u32 in, u32 out)
		{
		u32 x[16];

		memcpy(x, in, 64);

		chacha20_permute(x);

		memcpy(&out[0], &x[0], 16);
		memcpy(&out[4], &x[12], 16);
		}
		EXPORT_SYMBOL(hchacha20_block);