according to benchmarks speed up by about ~9% for pubkey computation

.cirrus.yml

@@ -22,6 +22,7 @@ env:
   RECOVERY: no
   SCHNORRSIG: no
   ELLSWIFT: no
+  SILENTPAYMENTS: no
   ### test options
   SECP256K1_TEST_ITERS:
   BENCH: yes
@@ -68,6 +69,7 @@ task:
     RECOVERY: yes
     SCHNORRSIG: yes
     ELLSWIFT: yes
+    SILENTPAYMENTS: yes
   matrix:
      # Currently only gcc-snapshot, the other compilers are tested on GHA with QEMU
      - env: { CC: 'gcc-snapshot' }
@@ -84,6 +86,7 @@ task:
     RECOVERY: yes
     SCHNORRSIG: yes
     ELLSWIFT: yes
+    SILENTPAYMENTS: yes
     WRAPPER_CMD: 'valgrind --error-exitcode=42'
     SECP256K1_TEST_ITERS: 2
   matrix:

.github/workflows/ci.yml

@@ -33,6 +33,7 @@ env:
   RECOVERY: 'no'
   SCHNORRSIG: 'no'
   ELLSWIFT: 'no'
+  SILENTPAYMENTS: 'no'
   ### test options
   SECP256K1_TEST_ITERS:
   BENCH: 'yes'
@@ -71,18 +72,18 @@ jobs:
       matrix:
         configuration:
           - env_vars: { WIDEMUL: 'int64',  RECOVERY: 'yes' }
-          - env_vars: { WIDEMUL: 'int64',                   ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes' }
+          - env_vars: { WIDEMUL: 'int64',                   ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes', SILENTPAYMENTS: 'yes' }
           - env_vars: { WIDEMUL: 'int128' }
           - env_vars: { WIDEMUL: 'int128_struct',                                           ELLSWIFT: 'yes' }
           - env_vars: { WIDEMUL: 'int128', RECOVERY: 'yes',              SCHNORRSIG: 'yes', ELLSWIFT: 'yes' }
-          - env_vars: { WIDEMUL: 'int128',                  ECDH: 'yes', SCHNORRSIG: 'yes' }
+          - env_vars: { WIDEMUL: 'int128',                  ECDH: 'yes', SCHNORRSIG: 'yes',                  SILENTPAYMENTS: 'yes' }
           - env_vars: { WIDEMUL: 'int128', ASM: 'x86_64',                                   ELLSWIFT: 'yes' }
           - env_vars: {                    RECOVERY: 'yes',              SCHNORRSIG: 'yes' }
-          - env_vars: { CTIMETESTS: 'no',  RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', CPPFLAGS: '-DVERIFY' }
+          - env_vars: { CTIMETESTS: 'no',  RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes',                  SILENTPAYMENTS: 'yes', CPPFLAGS: '-DVERIFY' }
           - env_vars: { BUILD: 'distcheck', WITH_VALGRIND: 'no', CTIMETESTS: 'no', BENCH: 'no' }
           - env_vars: { CPPFLAGS: '-DDETERMINISTIC' }
           - env_vars: { CFLAGS: '-O0', CTIMETESTS: 'no' }
-          - env_vars: { CFLAGS: '-O1',     RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes' }
+          - env_vars: { CFLAGS: '-O1',     RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes', SILENTPAYMENTS: 'yes' }
           - env_vars: { ECMULTGENPRECISION: 2, ECMULTWINDOW: 2 }
           - env_vars: { ECMULTGENPRECISION: 8, ECMULTWINDOW: 4 }
         cc:
@@ -141,6 +142,7 @@ jobs:
       RECOVERY: 'yes'
       SCHNORRSIG: 'yes'
       ELLSWIFT: 'yes'
+      SILENTPAYMENTS: 'yes'
       CC: ${{ matrix.cc }}
 
     steps:
@@ -185,6 +187,7 @@ jobs:
       RECOVERY: 'yes'
       SCHNORRSIG: 'yes'
       ELLSWIFT: 'yes'
+      SILENTPAYMENTS: 'yes'
       CTIMETESTS: 'no'
 
     steps:
@@ -236,6 +239,7 @@ jobs:
       RECOVERY: 'yes'
       SCHNORRSIG: 'yes'
       ELLSWIFT: 'yes'
+      SILENTPAYMENTS: 'yes'
       CTIMETESTS: 'no'
 
     steps:
@@ -281,6 +285,7 @@ jobs:
       RECOVERY: 'yes'
       SCHNORRSIG: 'yes'
       ELLSWIFT: 'yes'
+      SILENTPAYMENTS: 'yes'
       CTIMETESTS: 'no'
 
     strategy:
@@ -336,6 +341,7 @@ jobs:
       RECOVERY: 'yes'
       SCHNORRSIG: 'yes'
       ELLSWIFT: 'yes'
+      SILENTPAYMENTS: 'yes'
       CTIMETESTS: 'no'
 
     steps:
@@ -388,6 +394,7 @@ jobs:
       RECOVERY: 'yes'
       SCHNORRSIG: 'yes'
       ELLSWIFT: 'yes'
+      SILENTPAYMENTS: 'yes'
       CTIMETESTS: 'no'
       SECP256K1_TEST_ITERS: 2
 
@@ -439,6 +446,7 @@ jobs:
       RECOVERY: 'yes'
       SCHNORRSIG: 'yes'
       ELLSWIFT: 'yes'
+      SILENTPAYMENTS: 'yes'
       CTIMETESTS: 'no'
       CFLAGS: '-fsanitize=undefined,address -g'
       UBSAN_OPTIONS: 'print_stacktrace=1:halt_on_error=1'
@@ -496,6 +504,7 @@ jobs:
       RECOVERY: 'yes'
       SCHNORRSIG: 'yes'
       ELLSWIFT: 'yes'
+      SILENTPAYMENTS: 'yes'
       CTIMETESTS: 'yes'
       CC: 'clang'
       SECP256K1_TEST_ITERS: 32
@@ -543,6 +552,7 @@ jobs:
       RECOVERY: 'yes'
       SCHNORRSIG: 'yes'
       ELLSWIFT: 'yes'
+      SILENTPAYMENTS: 'yes'
       CTIMETESTS: 'no'
 
     strategy:
@@ -599,14 +609,14 @@ jobs:
       fail-fast: false
       matrix:
         env_vars:
-          - { WIDEMUL: 'int64',  RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes' }
+          - { WIDEMUL: 'int64',  RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes', SILENTPAYMENTS: 'yes' }
           - { WIDEMUL: 'int128_struct', ECMULTGENPRECISION: 2, ECMULTWINDOW: 4 }
-          - { WIDEMUL: 'int128',                  ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes' }
+          - { WIDEMUL: 'int128',                  ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes', SILENTPAYMENTS: 'yes' }
           - { WIDEMUL: 'int128', RECOVERY: 'yes' }
-          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes' }
-          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes', CC: 'gcc' }
-          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes',            WRAPPER_CMD: 'valgrind --error-exitcode=42', SECP256K1_TEST_ITERS: 2 }
-          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes', CC: 'gcc', WRAPPER_CMD: 'valgrind --error-exitcode=42', SECP256K1_TEST_ITERS: 2 }
+          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes', SILENTPAYMENTS: 'yes' }
+          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes', SILENTPAYMENTS: 'yes', CC: 'gcc' }
+          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes', SILENTPAYMENTS: 'yes',            WRAPPER_CMD: 'valgrind --error-exitcode=42', SECP256K1_TEST_ITERS: 2 }
+          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes', SILENTPAYMENTS: 'yes', CC: 'gcc', WRAPPER_CMD: 'valgrind --error-exitcode=42', SECP256K1_TEST_ITERS: 2 }
           - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', SCHNORRSIG: 'yes', ELLSWIFT: 'yes', CPPFLAGS: '-DVERIFY', CTIMETESTS: 'no' }
           - BUILD: 'distcheck'
 
@@ -718,6 +728,7 @@ jobs:
       RECOVERY: 'yes'
       SCHNORRSIG: 'yes'
       ELLSWIFT: 'yes'
+      SILENTPAYMENTS: 'yes'
 
     steps:
       - name: Checkout

CMakeLists.txt

@@ -60,9 +60,14 @@ option(SECP256K1_ENABLE_MODULE_RECOVERY "Enable ECDSA pubkey recovery module." O
 option(SECP256K1_ENABLE_MODULE_EXTRAKEYS "Enable extrakeys module." ON)
 option(SECP256K1_ENABLE_MODULE_SCHNORRSIG "Enable schnorrsig module." ON)
 option(SECP256K1_ENABLE_MODULE_ELLSWIFT "Enable ElligatorSwift module." ON)
+option(SECP256K1_ENABLE_MODULE_SILENTPAYMENTS "Enable Silent Payments module." OFF)
 
 # Processing must be done in a topological sorting of the dependency graph
 # (dependent module first).
+if(SECP256K1_ENABLE_MODULE_SILENTPAYMENTS)
+  add_compile_definitions(ENABLE_MODULE_SILENTPAYMENTS=1)
+endif()
+
 if(SECP256K1_ENABLE_MODULE_ELLSWIFT)
   add_compile_definitions(ENABLE_MODULE_ELLSWIFT=1)
 endif()
@@ -292,6 +297,7 @@ message("  ECDSA pubkey recovery ............... ${SECP256K1_ENABLE_MODULE_RECOV
 message("  extrakeys ........................... ${SECP256K1_ENABLE_MODULE_EXTRAKEYS}")
 message("  schnorrsig .......................... ${SECP256K1_ENABLE_MODULE_SCHNORRSIG}")
 message("  ElligatorSwift ...................... ${SECP256K1_ENABLE_MODULE_ELLSWIFT}")
+message("  Silent Payments ..................... ${SECP256K1_ENABLE_MODULE_SILENTPAYMENTS}")
 message("Parameters:")
 message("  ecmult window size .................. ${SECP256K1_ECMULT_WINDOW_SIZE}")
 message("  ecmult gen precision bits ........... ${SECP256K1_ECMULT_GEN_PREC_BITS}")

Makefile.am

@@ -64,6 +64,8 @@ noinst_HEADERS += src/field.h
 noinst_HEADERS += src/field_impl.h
 noinst_HEADERS += src/bench.h
 noinst_HEADERS += src/wycheproof/ecdsa_secp256k1_sha256_bitcoin_test.h
+noinst_HEADERS += src/hsort.h
+noinst_HEADERS += src/hsort_impl.h
 noinst_HEADERS += contrib/lax_der_parsing.h
 noinst_HEADERS += contrib/lax_der_parsing.c
 noinst_HEADERS += contrib/lax_der_privatekey_parsing.h
@@ -271,3 +273,7 @@ endif
 if ENABLE_MODULE_ELLSWIFT
 include src/modules/ellswift/Makefile.am.include
 endif
+
+if ENABLE_MODULE_SILENTPAYMENTS
+include src/modules/silentpayments/Makefile.am.include
+endif

ci/ci.sh

@@ -13,7 +13,7 @@ print_environment() {
     # does not rely on bash.
     for var in WERROR_CFLAGS MAKEFLAGS BUILD \
             ECMULTWINDOW ECMULTGENPRECISION ASM WIDEMUL WITH_VALGRIND EXTRAFLAGS \
-            EXPERIMENTAL ECDH RECOVERY SCHNORRSIG ELLSWIFT \
+            EXPERIMENTAL ECDH RECOVERY SCHNORRSIG ELLSWIFT SILENTPAYMENTS \
             SECP256K1_TEST_ITERS BENCH SECP256K1_BENCH_ITERS CTIMETESTS\
             EXAMPLES \
             HOST WRAPPER_CMD \
@@ -76,6 +76,7 @@ esac
     --with-ecmult-gen-precision="$ECMULTGENPRECISION" \
     --enable-module-ecdh="$ECDH" --enable-module-recovery="$RECOVERY" \
     --enable-module-ellswift="$ELLSWIFT" \
+    --enable-module-silentpayments="$SILENTPAYMENTS" \
     --enable-module-schnorrsig="$SCHNORRSIG" \
     --enable-examples="$EXAMPLES" \
     --enable-ctime-tests="$CTIMETESTS" \

configure.ac

@@ -188,6 +188,10 @@ AC_ARG_ENABLE(module_ellswift,
     AS_HELP_STRING([--enable-module-ellswift],[enable ElligatorSwift module [default=yes]]), [],
     [SECP_SET_DEFAULT([enable_module_ellswift], [yes], [yes])])
 
+AC_ARG_ENABLE(module_silentpayments,
+    AS_HELP_STRING([--enable-module-silentpayments],[enable Silent Payments module [default=no]]), [],
+    [SECP_SET_DEFAULT([enable_module_silentpayments], [no], [yes])])
+
 AC_ARG_ENABLE(external_default_callbacks,
     AS_HELP_STRING([--enable-external-default-callbacks],[enable external default callback functions [default=no]]), [],
     [SECP_SET_DEFAULT([enable_external_default_callbacks], [no], [no])])
@@ -389,6 +393,10 @@ SECP_CFLAGS="$SECP_CFLAGS $WERROR_CFLAGS"
 
 # Processing must be done in a reverse topological sorting of the dependency graph
 # (dependent module first).
+if test x"$enable_module_silentpayments" = x"yes"; then
+  SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_SILENTPAYMENTS=1"
+fi
+
 if test x"$enable_module_ellswift" = x"yes"; then
   SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_ELLSWIFT=1"
 fi
@@ -450,6 +458,7 @@ AM_CONDITIONAL([ENABLE_MODULE_RECOVERY], [test x"$enable_module_recovery" = x"ye
 AM_CONDITIONAL([ENABLE_MODULE_EXTRAKEYS], [test x"$enable_module_extrakeys" = x"yes"])
 AM_CONDITIONAL([ENABLE_MODULE_SCHNORRSIG], [test x"$enable_module_schnorrsig" = x"yes"])
 AM_CONDITIONAL([ENABLE_MODULE_ELLSWIFT], [test x"$enable_module_ellswift" = x"yes"])
+AM_CONDITIONAL([ENABLE_MODULE_SILENTPAYMENTS], [test x"$enable_module_silentpayments" = x"yes"])
 AM_CONDITIONAL([USE_EXTERNAL_ASM], [test x"$enable_external_asm" = x"yes"])
 AM_CONDITIONAL([USE_ASM_ARM], [test x"$set_asm" = x"arm32"])
 AM_CONDITIONAL([BUILD_WINDOWS], [test "$build_windows" = "yes"])
@@ -472,6 +481,7 @@ echo "  module recovery         = $enable_module_recovery"
 echo "  module extrakeys        = $enable_module_extrakeys"
 echo "  module schnorrsig       = $enable_module_schnorrsig"
 echo "  module ellswift         = $enable_module_ellswift"
+echo "  module silentpayments   = $enable_module_silentpayments"
 echo
 echo "  asm                     = $set_asm"
 echo "  ecmult window size      = $set_ecmult_window"

include/secp256k1.h

@@ -474,6 +474,20 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_cmp(
     const secp256k1_pubkey *pubkey2
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
+/** Sort public keys keys using lexicographic (of compressed serialization) order
+ *
+ *  Returns: 0 if the arguments are invalid. 1 otherwise.
+ *
+ *  Args:     ctx: pointer to a context object
+ *  In:   pubkeys: array of pointers to pubkeys to sort
+ *      n_pubkeys: number of elements in the pubkeys array
+ */
+SECP256K1_API int secp256k1_ec_pubkey_sort(
+    const secp256k1_context *ctx,
+    const secp256k1_pubkey **pubkeys,
+    size_t n_pubkeys
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
+
 /** Parse an ECDSA signature in compact (64 bytes) format.
  *
  *  Returns: 1 when the signature could be parsed, 0 otherwise.