@@ -9,7 +9,7 @@
* Adiantum is a tweakable, length-preserving encryption mode designed for fast
* and secure disk encryption, especially on CPUs without dedicated crypto
* instructions. Adiantum encrypts each sector using the XChaCha12 stream
- * cipher, two passes of an ε-almost-∆-universal (εA∆U) hash function based on
+ * cipher, two passes of an ε-almost-∆-universal (ε-∆U) hash function based on
* NH and Poly1305, and an invocation of the AES-256 block cipher on a single
* 16-byte block. See the paper for details:
*
@@ -21,12 +21,12 @@
* - Stream cipher: XChaCha12 or XChaCha20
* - Block cipher: any with a 128-bit block size and 256-bit key
*
- * This implementation doesn't currently allow other εA∆U hash functions, i.e.
+ * This implementation doesn't currently allow other ε-∆U hash functions, i.e.
* HPolyC is not supported. This is because Adiantum is ~20% faster than HPolyC
- * but still provably as secure, and also the εA∆U hash function of HBSH is
+ * but still provably as secure, and also the ε-∆U hash function of HBSH is
* formally defined to take two inputs (tweak, message) which makes it difficult
* to wrap with the crypto_shash API. Rather, some details need to be handled
- * here. Nevertheless, if needed in the future, support for other εA∆U hash
+ * here. Nevertheless, if needed in the future, support for other ε-∆U hash
* functions could be added here.
*/
@@ -41,7 +41,7 @@
#include "internal.h"
/*
- * Size of right-hand block of input data, in bytes; also the size of the block
+ * Size of right-hand part of input data, in bytes; also the size of the block
* cipher's block size and the hash function's output.
*/
#define BLOCKCIPHER_BLOCK_SIZE 16
@@ -77,7 +77,7 @@ struct adiantum_tfm_ctx {
struct adiantum_request_ctx {
/*
- * Buffer for right-hand block of data, i.e.
+ * Buffer for right-hand part of data, i.e.
*
* P_L => P_M => C_M => C_R when encrypting, or
* C_R => C_M => P_M => P_L when decrypting.
@@ -93,8 +93,8 @@ struct adiantum_request_ctx {
bool enc; /* true if encrypting, false if decrypting */
/*
- * The result of the Poly1305 εA∆U hash function applied to
- * (message length, tweak).
+ * The result of the Poly1305 ε-∆U hash function applied to
+ * (bulk length, tweak)
*/
le128 header_hash;
@@ -213,13 +213,16 @@ static inline void le128_sub(le128 *r, const le128 *v1, const le128 *v2)
}
/*
- * Apply the Poly1305 εA∆U hash function to (message length, tweak) and save the
- * result to rctx->header_hash.
+ * Apply the Poly1305 ε-∆U hash function to (bulk length, tweak) and save the
+ * result to rctx->header_hash. This is the calculation
*
- * This value is reused in both the first and second hash steps. Specifically,
- * it's added to the result of an independently keyed εA∆U hash function (for
- * equal length inputs only) taken over the message. This gives the overall
- * Adiantum hash of the (tweak, message) pair.
+ * H_T ← Poly1305_{K_T}(bin_{128}(|L|) || T)
+ *
+ * from the procedure in section 6.4 of the Adiantum paper. The resulting value
+ * is reused in both the first and second hash steps. Specifically, it's added
+ * to the result of an independently keyed ε-∆U hash function (for equal length
+ * inputs only) taken over the left-hand part (the "bulk") of the message, to
+ * give the overall Adiantum hash of the (tweak, left-hand part) pair.
*/
static void adiantum_hash_header(struct skcipher_request *req)
{
@@ -248,7 +251,7 @@ static void adiantum_hash_header(struct skcipher_request *req)
poly1305_core_emit(&state, &rctx->header_hash);
}
-/* Hash the left-hand block (the "bulk") of the message using NHPoly1305 */
+/* Hash the left-hand part (the "bulk") of the message using NHPoly1305 */
static int adiantum_hash_message(struct skcipher_request *req,
struct scatterlist *sgl, le128 *digest)
{
@@ -550,7 +553,7 @@ static int adiantum_create(struct crypto_template *tmpl, struct rtattr **tb)
goto out_drop_streamcipher;
blockcipher_alg = ictx->blockcipher_spawn.alg;
- /* NHPoly1305 εA∆U hash function */
+ /* NHPoly1305 ε-∆U hash function */
_hash_alg = crypto_alg_mod_lookup(nhpoly1305_name,
CRYPTO_ALG_TYPE_SHASH,
CRYPTO_ALG_TYPE_MASK);
@@ -9,15 +9,15 @@
* "NHPoly1305" is the main component of Adiantum hashing.
* Specifically, it is the calculation
*
- * H_M ← Poly1305_{K_M}(NH_{K_N}(pad_{128}(M)))
+ * H_L ← Poly1305_{K_L}(NH_{K_N}(pad_{128}(L)))
*
- * from the procedure in section A.5 of the Adiantum paper [1]. It is an
- * ε-almost-∆-universal (εA∆U) hash function for equal-length inputs over
+ * from the procedure in section 6.4 of the Adiantum paper [1]. It is an
+ * ε-almost-∆-universal (ε-∆U) hash function for equal-length inputs over
* Z/(2^{128}Z), where the "∆" operation is addition. It hashes 1024-byte
* chunks of the input with the NH hash function [2], reducing the input length
* by 32x. The resulting NH digests are evaluated as a polynomial in
* GF(2^{130}-5), like in the Poly1305 MAC [3]. Note that the polynomial
- * evaluation by itself would suffice to achieve the εA∆U property; NH is used
+ * evaluation by itself would suffice to achieve the ε-∆U property; NH is used
* for performance since it's over twice as fast as Poly1305.
*
* This is *not* a cryptographic hash function; do not use it as such!