From f5e815f4306ea1763d27d83646b4f06e3d2f0b94 Mon Sep 17 00:00:00 2001
From: Sebastian Falbesoner <sebastian.falbesoner@gmail.com>
Date: Mon, 17 Nov 2025 18:35:32 +0100
Subject: [PATCH] remove secp256k1_eckey_pubkey_serialize function

---
 src/eckey.h      |  1 -
 src/eckey_impl.h | 20 --------------------
 src/tests.c      | 23 +++++++++--------------
 3 files changed, 9 insertions(+), 35 deletions(-)

diff --git a/src/eckey.h b/src/eckey.h
index 3ebe8969..c2bbc470 100644
--- a/src/eckey.h
+++ b/src/eckey.h
@@ -15,7 +15,6 @@
 #include "ecmult_gen.h"
 
 static int secp256k1_eckey_pubkey_parse(secp256k1_ge *elem, const unsigned char *pub, size_t size);
-static int secp256k1_eckey_pubkey_serialize(secp256k1_ge *elem, unsigned char *pub, size_t *size, int compressed);
 /** Serialize a group element (that is not allowed to be infinity) to a compressed public key (33 bytes). */
 static void secp256k1_eckey_pubkey_serialize33(secp256k1_ge *elem, unsigned char *pub33);
 /** Serialize a group element (that is not allowed to be infinity) to an uncompressed public key (65 bytes). */
diff --git a/src/eckey_impl.h b/src/eckey_impl.h
index 4f647607..48745e8f 100644
--- a/src/eckey_impl.h
+++ b/src/eckey_impl.h
@@ -35,26 +35,6 @@ static int secp256k1_eckey_pubkey_parse(secp256k1_ge *elem, const unsigned char
     }
 }
 
-static int secp256k1_eckey_pubkey_serialize(secp256k1_ge *elem, unsigned char *pub, size_t *size, int compressed) {
-    VERIFY_CHECK(compressed == 0 || compressed == 1);
-
-    if (secp256k1_ge_is_infinity(elem)) {
-        return 0;
-    }
-    secp256k1_fe_normalize_var(&elem->x);
-    secp256k1_fe_normalize_var(&elem->y);
-    secp256k1_fe_get_b32(&pub[1], &elem->x);
-    if (compressed) {
-        *size = 33;
-        pub[0] = secp256k1_fe_is_odd(&elem->y) ? SECP256K1_TAG_PUBKEY_ODD : SECP256K1_TAG_PUBKEY_EVEN;
-    } else {
-        *size = 65;
-        pub[0] = SECP256K1_TAG_PUBKEY_UNCOMPRESSED;
-        secp256k1_fe_get_b32(&pub[33], &elem->y);
-    }
-    return 1;
-}
-
 static void secp256k1_eckey_pubkey_serialize33(secp256k1_ge *elem, unsigned char *pub33) {
     VERIFY_CHECK(!secp256k1_ge_is_infinity(elem));
 
diff --git a/src/tests.c b/src/tests.c
index 0ccdbeec..4029de56 100644
--- a/src/tests.c
+++ b/src/tests.c
@@ -4315,8 +4315,6 @@ static void test_point_times_order(const secp256k1_gej *point) {
     secp256k1_scalar nx;
     secp256k1_gej res1, res2;
     secp256k1_ge res3;
-    unsigned char pub[65];
-    size_t psize = 65;
     testutil_random_scalar_order_test(&x);
     secp256k1_scalar_negate(&nx, &x);
     secp256k1_ecmult(&res1, point, &x, &x); /* calc res1 = x * point + x * G; */
@@ -4326,9 +4324,6 @@ static void test_point_times_order(const secp256k1_gej *point) {
     secp256k1_ge_set_gej(&res3, &res1);
     CHECK(secp256k1_ge_is_infinity(&res3));
     CHECK(secp256k1_ge_is_valid_var(&res3) == 0);
-    CHECK(secp256k1_eckey_pubkey_serialize(&res3, pub, &psize, 0) == 0);
-    psize = 65;
-    CHECK(secp256k1_eckey_pubkey_serialize(&res3, pub, &psize, 1) == 0);
     /* check zero/one edge cases */
     secp256k1_ecmult(&res1, point, &secp256k1_scalar_zero, &secp256k1_scalar_zero);
     secp256k1_ge_set_gej(&res3, &res1);
@@ -5435,7 +5430,6 @@ static void test_ecmult_accumulate(secp256k1_sha256* acc, const secp256k1_scalar
     secp256k1_gej rj1, rj2, rj3, rj4, rj5, rj6, gj, infj;
     secp256k1_ge r;
     unsigned char bytes[65];
-    size_t size = 65;
     secp256k1_gej_set_ge(&gj, &secp256k1_ge_const_g);
     secp256k1_gej_set_infinity(&infj);
     secp256k1_ecmult_gen(&CTX->ecmult_gen_ctx, &rj1, x);
@@ -5456,9 +5450,8 @@ static void test_ecmult_accumulate(secp256k1_sha256* acc, const secp256k1_scalar
         secp256k1_sha256_write(acc, zerobyte, 1);
     } else {
         /* Store other points using their uncompressed serialization. */
-        secp256k1_eckey_pubkey_serialize(&r, bytes, &size, 0);
-        CHECK(size == 65);
-        secp256k1_sha256_write(acc, bytes, size);
+        secp256k1_eckey_pubkey_serialize65(&r, bytes);
+        secp256k1_sha256_write(acc, bytes, sizeof(bytes));
     }
 }
 
@@ -6543,16 +6536,18 @@ static void test_random_pubkeys(void) {
         size_t size = len;
         firstb = in[0];
         /* If the pubkey can be parsed, it should round-trip... */
-        CHECK(secp256k1_eckey_pubkey_serialize(&elem, out, &size, len == 33));
-        CHECK(size == len);
+        if (len == 33) {
+            secp256k1_eckey_pubkey_serialize33(&elem, out);
+        } else {
+            secp256k1_eckey_pubkey_serialize65(&elem, out);
+        }
         CHECK(secp256k1_memcmp_var(&in[1], &out[1], len-1) == 0);
         /* ... except for the type of hybrid inputs. */
         if ((in[0] != 6) && (in[0] != 7)) {
             CHECK(in[0] == out[0]);
         }
         size = 65;
-        CHECK(secp256k1_eckey_pubkey_serialize(&elem, in, &size, 0));
-        CHECK(size == 65);
+        secp256k1_eckey_pubkey_serialize65(&elem, in);
         CHECK(secp256k1_eckey_pubkey_parse(&elem2, in, size));
         CHECK(secp256k1_ge_eq_var(&elem2, &elem));
         /* Check that the X9.62 hybrid type is checked. */
@@ -6567,7 +6562,7 @@ static void test_random_pubkeys(void) {
         }
         if (res) {
             CHECK(secp256k1_ge_eq_var(&elem, &elem2));
-            CHECK(secp256k1_eckey_pubkey_serialize(&elem, out, &size, 0));
+            secp256k1_eckey_pubkey_serialize65(&elem, out);
             CHECK(secp256k1_memcmp_var(&in[1], &out[1], 64) == 0);
         }
     }