From: Nick Mathewson <nickm@torproject.org>
Date: Sun, 20 Apr 2025 14:37:38 +0000 (-0400)
Subject: Polyval: add ability to store key separately.
X-Git-Tag: tor-0.4.9.3-alpha~49^2~8
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=3aa29c52b6a4dba599ab75310f3c639874e7f22a;p=thirdparty%2Ftor.git

Polyval: add ability to store key separately.

This will help reduce storage, since we never actually need
to keep a running total outside of a function.
---

diff --git a/src/ext/polyval/ctmul.c b/src/ext/polyval/ctmul.c
index b4bfa25bce..f408b580a3 100644
--- a/src/ext/polyval/ctmul.c
+++ b/src/ext/polyval/ctmul.c
@@ -197,7 +197,7 @@ static void
 pv_mul_y_h(polyval_t *pv)
 {
 	uint32_t *yw = pv->y.v;
-	const uint32_t *hw = pv->h.v;
+	const uint32_t *hw = pv->key.h.v;
 
 	/*
 	 * Throughout the loop we handle the y and h values as arrays
diff --git a/src/ext/polyval/ctmul64.c b/src/ext/polyval/ctmul64.c
index c2205953a3..1b10aa196f 100644
--- a/src/ext/polyval/ctmul64.c
+++ b/src/ext/polyval/ctmul64.c
@@ -80,11 +80,11 @@ pv_mul_y_h(polyval_t *pv)
 
 	y0 = pv->y.lo;
 	y1 = pv->y.hi;
-	h0 = pv->h.lo;
-	h1 = pv->h.hi;
+	h0 = pv->key.h.lo;
+	h1 = pv->key.h.hi;
 	// TODO(nm) does it actually make sense for us to precompute this?
-	h0r = pv->hr.lo;
-	h1r = pv->hr.hi;
+	h0r = pv->key.hr.lo;
+	h1r = pv->key.hr.hi;
 
 	h2 = h0 ^ h1;
 	h2r = h0r ^ h1r;
diff --git a/src/ext/polyval/pclmul.c b/src/ext/polyval/pclmul.c
index 5a10c1e29a..2248aa6fcb 100644
--- a/src/ext/polyval/pclmul.c
+++ b/src/ext/polyval/pclmul.c
@@ -156,7 +156,7 @@ void pv_mul_y_h(polyval_t *pv)
 {
 	__m128i yw, h1w, h1x;
 
-        h1w = pv->h;
+        h1w = pv->key.h;
         BK(h1w, h1x);
 
         {
diff --git a/src/ext/polyval/polyval.c b/src/ext/polyval/polyval.c
index e0e0c6d597..cc31a92be9 100644
--- a/src/ext/polyval/polyval.c
+++ b/src/ext/polyval/polyval.c
@@ -66,7 +66,7 @@ static inline void pv_xor_y(polyval_t *, u128 v);
 /**
  * Initialize any derived fields in pv.
  */
-static inline void pv_init_extra(polyval_t *pv);
+static inline void pv_init_extra(polyval_key_t *pv);
 
 /* ========
  * The function which we expect our backend to implement.
@@ -140,7 +140,7 @@ pv_xor_y(polyval_t *pv, u128 v)
   pv->y = _mm_xor_si128(pv->y, v);
 }
 static inline void
-pv_init_extra(polyval_t *pv)
+pv_init_extra(polyval_key_t *pv)
 {
   (void)pv;
 }
@@ -173,7 +173,7 @@ pv_xor_y(polyval_t *pv, u128 val)
   pv->y.hi ^= val.hi;
 }
 static inline void
-pv_init_extra(polyval_t *pv)
+pv_init_extra(polyval_key_t *pv)
 {
   pv->hr.lo = rev64(pv->h.lo);
   pv->hr.hi = rev64(pv->h.hi);
@@ -208,18 +208,29 @@ pv_xor_y(polyval_t *pv, u128 val)
   }
 }
 static inline void
-pv_init_extra(polyval_t *pv)
+pv_init_extra(polyval_key_t *pv)
 {
   (void)pv;
 }
 #endif
 
+void
+polyval_key_init(polyval_key_t *pvk, const uint8_t *key)
+{
+  pvk->h = u128_from_bytes(key);
+  pv_init_extra(pvk);
+}
 void
 polyval_init(polyval_t *pv, const uint8_t *key)
 {
-  pv->h = u128_from_bytes(key);
+  polyval_key_init(&pv->key, key);
+  memset(&pv->y, 0, sizeof(u128));
+}
+void
+polyval_init_from_key(polyval_t *pv, const polyval_key_t *key)
+{
+  memcpy(&pv->key, key, sizeof(polyval_key_t));
   memset(&pv->y, 0, sizeof(u128));
-  pv_init_extra(pv);
 }
 void
 polyval_add_block(polyval_t *pv, const uint8_t *block)
diff --git a/src/ext/polyval/polyval.h b/src/ext/polyval/polyval.h
index 3a137794c6..5bfaae1e88 100644
--- a/src/ext/polyval/polyval.h
+++ b/src/ext/polyval/polyval.h
@@ -54,17 +54,22 @@ typedef struct pv_u128_ {
 } pv_u128_;
 #endif
 
-/**
- * State for an instance of the polyval hash.
- **/
-typedef struct polyval_t {
-  /** The key itself. */
+/** A key for a polyval hash, plus any precomputed key material. */
+typedef struct polyval_key_t {
   pv_u128_ h;
 #ifdef PV_USE_CTMUL64
   /** The elements of the key in bit-reversed form.
    * (Used as an optimization.) */
   pv_u128_ hr;
 #endif
+} polyval_key_t;
+
+/**
+ * State for an instance of the polyval hash.
+ **/
+typedef struct polyval_t {
+  /** The key used for this instance of polyval. */
+  polyval_key_t key;
   /** The accumulator */
   pv_u128_ y;
 } polyval_t;
@@ -82,10 +87,18 @@ typedef struct polyval_t {
  */
 #define POLYVAL_TAG_LEN 16
 
+/** Do any necessary precomputation from a polyval key,
+ * and store it.
+ */
+void polyval_key_init(polyval_key_t *, const uint8_t *key);
 /**
  * Initialize a polyval instance with a given key.
  */
 void polyval_init(polyval_t *, const uint8_t *key);
+/**
+ * Initialize a polyval instance with a preconstructed key.
+ */
+void polyval_init_from_key(polyval_t *, const polyval_key_t *key);
 /**
  * Update a polyval instance with a new 16-byte block.
  */