Add schnorrsig module which implements BIP-340 compliant signatures

.gitignore

@@ -1,9 +1,9 @@
 bench_inv
 bench_ecdh
 bench_ecmult
+bench_schnorrsig
 bench_sign
 bench_verify
-bench_schnorr_verify
 bench_recover
 bench_internal
 tests

.travis.yml

@@ -17,19 +17,19 @@ compiler:
   - gcc
 env:
   global:
-    - WIDEMUL=auto  BIGNUM=auto  ENDOMORPHISM=no  STATICPRECOMPUTATION=yes  ECMULTGENPRECISION=auto  ASM=no  BUILD=check  EXTRAFLAGS=  HOST=  ECDH=no  RECOVERY=no  EXPERIMENTAL=no CTIMETEST=yes BENCH=yes ITERS=2
+    - WIDEMUL=auto  BIGNUM=auto  ENDOMORPHISM=no  STATICPRECOMPUTATION=yes  ECMULTGENPRECISION=auto  ASM=no  BUILD=check  EXTRAFLAGS=  HOST=  ECDH=no  RECOVERY=no SCHNORRSIG=no EXPERIMENTAL=no CTIMETEST=yes BENCH=yes ITERS=2
   matrix:
     - WIDEMUL=int64   RECOVERY=yes
-    - WIDEMUL=int64   ECDH=yes  EXPERIMENTAL=yes
+    - WIDEMUL=int64   ECDH=yes  EXPERIMENTAL=yes SCHNORRSIG=yes
     - WIDEMUL=int64   ENDOMORPHISM=yes
     - WIDEMUL=int128
-    - WIDEMUL=int128  RECOVERY=yes
+    - WIDEMUL=int128  RECOVERY=yes EXPERIMENTAL=yes SCHNORRSIG=yes
     - WIDEMUL=int128  ENDOMORPHISM=yes
-    - WIDEMUL=int128  ENDOMORPHISM=yes  ECDH=yes EXPERIMENTAL=yes
+    - WIDEMUL=int128  ENDOMORPHISM=yes  ECDH=yes EXPERIMENTAL=yes SCHNORRSIG=yes
     - WIDEMUL=int128                    ASM=x86_64
     - WIDEMUL=int128  ENDOMORPHISM=yes  ASM=x86_64
     - BIGNUM=no
-    - BIGNUM=no       ENDOMORPHISM=yes RECOVERY=yes EXPERIMENTAL=yes
+    - BIGNUM=no       ENDOMORPHISM=yes RECOVERY=yes EXPERIMENTAL=yes SCHNORRSIG=yes
     - BIGNUM=no       STATICPRECOMPUTATION=no
     - BUILD=distcheck CTIMETEST= BENCH=
     - CPPFLAGS=-DDETERMINISTIC

Makefile.am

@@ -153,3 +153,11 @@ endif
 if ENABLE_MODULE_RECOVERY
 include src/modules/recovery/Makefile.am.include
 endif
+
+if ENABLE_MODULE_EXTRAKEYS
+include src/modules/extrakeys/Makefile.am.include
+endif
+
+if ENABLE_MODULE_SCHNORRSIG
+include src/modules/schnorrsig/Makefile.am.include
+endif

configure.ac

@@ -136,6 +136,16 @@ AC_ARG_ENABLE(module_recovery,
     [enable_module_recovery=$enableval],
     [enable_module_recovery=no])
 
+AC_ARG_ENABLE(module_extrakeys,
+    AS_HELP_STRING([--enable-module-extrakeys],[enable extrakeys module (experimental)]),
+    [enable_module_extrakeys=$enableval],
+    [enable_module_extrakeys=no])
+
+AC_ARG_ENABLE(module_schnorrsig,
+    AS_HELP_STRING([--enable-module-schnorrsig],[enable schnorrsig module (experimental)]),
+    [enable_module_schnorrsig=$enableval],
+    [enable_module_schnorrsig=no])
+
 AC_ARG_ENABLE(external_default_callbacks,
     AS_HELP_STRING([--enable-external-default-callbacks],[enable external default callback functions [default=no]]),
     [use_external_default_callbacks=$enableval],
@@ -421,6 +431,17 @@ if test x"$enable_module_recovery" = x"yes"; then
   AC_DEFINE(ENABLE_MODULE_RECOVERY, 1, [Define this symbol to enable the ECDSA pubkey recovery module])
 fi
 
+if test x"$enable_module_schnorrsig" = x"yes"; then
+  AC_DEFINE(ENABLE_MODULE_SCHNORRSIG, 1, [Define this symbol to enable the schnorrsig module])
+  enable_module_extrakeys=yes
+fi
+
+# Test if extrakeys is set after the schnorrsig module to allow the schnorrsig
+# module to set enable_module_extrakeys=yes
+if test x"$enable_module_extrakeys" = x"yes"; then
+  AC_DEFINE(ENABLE_MODULE_EXTRAKEYS, 1, [Define this symbol to enable the extrakeys module])
+fi
+
 if test x"$use_external_asm" = x"yes"; then
   AC_DEFINE(USE_EXTERNAL_ASM, 1, [Define this symbol if an external (non-inline) assembly implementation is used])
 fi
@@ -434,11 +455,19 @@ if test x"$enable_experimental" = x"yes"; then
   AC_MSG_NOTICE([WARNING: experimental build])
   AC_MSG_NOTICE([Experimental features do not have stable APIs or properties, and may not be safe for production use.])
   AC_MSG_NOTICE([Building ECDH module: $enable_module_ecdh])
+  AC_MSG_NOTICE([Building extrakeys module: $enable_module_extrakeys])
+  AC_MSG_NOTICE([Building schnorrsig module: $enable_module_schnorrsig])
   AC_MSG_NOTICE([******])
 else
   if test x"$enable_module_ecdh" = x"yes"; then
     AC_MSG_ERROR([ECDH module is experimental. Use --enable-experimental to allow.])
   fi
+  if test x"$enable_module_extrakeys" = x"yes"; then
+    AC_MSG_ERROR([extrakeys module is experimental. Use --enable-experimental to allow.])
+  fi
+  if test x"$enable_module_schnorrsig" = x"yes"; then
+    AC_MSG_ERROR([schnorrsig module is experimental. Use --enable-experimental to allow.])
+  fi
   if test x"$set_asm" = x"arm"; then
     AC_MSG_ERROR([ARM assembly optimization is experimental. Use --enable-experimental to allow.])
   fi
@@ -457,6 +486,8 @@ AM_CONDITIONAL([USE_BENCHMARK], [test x"$use_benchmark" = x"yes"])
 AM_CONDITIONAL([USE_ECMULT_STATIC_PRECOMPUTATION], [test x"$set_precomp" = x"yes"])
 AM_CONDITIONAL([ENABLE_MODULE_ECDH], [test x"$enable_module_ecdh" = x"yes"])
 AM_CONDITIONAL([ENABLE_MODULE_RECOVERY], [test x"$enable_module_recovery" = x"yes"])
+AM_CONDITIONAL([ENABLE_MODULE_EXTRAKEYS], [test x"$enable_module_extrakeys" = x"yes"])
+AM_CONDITIONAL([ENABLE_MODULE_SCHNORRSIG], [test x"$enable_module_schnorrsig" = x"yes"])
 AM_CONDITIONAL([USE_EXTERNAL_ASM], [test x"$use_external_asm" = x"yes"])
 AM_CONDITIONAL([USE_ASM_ARM], [test x"$set_asm" = x"arm"])
 
@@ -476,6 +507,8 @@ echo "  with benchmarks         = $use_benchmark"
 echo "  with coverage           = $enable_coverage"
 echo "  module ecdh             = $enable_module_ecdh"
 echo "  module recovery         = $enable_module_recovery"
+echo "  module extrakeys        = $enable_module_extrakeys"
+echo "  module schnorrsig       = $enable_module_schnorrsig"
 echo
 echo "  asm                     = $set_asm"
 echo "  bignum                  = $set_bignum"

contrib/travis.sh

@@ -17,6 +17,7 @@ fi
     --with-test-override-wide-multiply="$WIDEMUL" --with-bignum="$BIGNUM" --with-asm="$ASM" \
     --enable-ecmult-static-precomputation="$STATICPRECOMPUTATION" --with-ecmult-gen-precision="$ECMULTGENPRECISION" \
     --enable-module-ecdh="$ECDH" --enable-module-recovery="$RECOVERY" \
+    --enable-module-schnorrsig="$SCHNORRSIG" \
     --host="$HOST" $EXTRAFLAGS
 
 if [ -n "$BUILD" ]

include/secp256k1_extrakeys.h

@@ -0,0 +1,236 @@
+#ifndef SECP256K1_EXTRAKEYS_H
+#define SECP256K1_EXTRAKEYS_H
+
+#include "secp256k1.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** Opaque data structure that holds a parsed and valid "x-only" public key.
+ *  An x-only pubkey encodes a point whose Y coordinate is even. It is
+ *  serialized using only its X coordinate (32 bytes). See BIP-340 for more
+ *  information about x-only pubkeys.
+ *
+ *  The exact representation of data inside is implementation defined and not
+ *  guaranteed to be portable between different platforms or versions. It is
+ *  however guaranteed to be 64 bytes in size, and can be safely copied/moved.
+ *  If you need to convert to a format suitable for storage, transmission, or
+ *  comparison, use secp256k1_xonly_pubkey_serialize and
+ *  secp256k1_xonly_pubkey_parse.
+ */
+typedef struct {
+    unsigned char data[64];
+} secp256k1_xonly_pubkey;
+
+/** Opaque data structure that holds a keypair consisting of a secret and a
+ *  public key.
+ *
+ *  The exact representation of data inside is implementation defined and not
+ *  guaranteed to be portable between different platforms or versions. It is
+ *  however guaranteed to be 96 bytes in size, and can be safely copied/moved.
+ */
+typedef struct {
+    unsigned char data[96];
+} secp256k1_keypair;
+
+/** Parse a 32-byte sequence into a xonly_pubkey object.
+ *
+ *  Returns: 1 if the public key was fully valid.
+ *           0 if the public key could not be parsed or is invalid.
+ *
+ *  Args:   ctx: a secp256k1 context object (cannot be NULL).
+ *  Out: pubkey: pointer to a pubkey object. If 1 is returned, it is set to a
+ *               parsed version of input. If not, it's set to an invalid value.
+ *               (cannot be NULL).
+ *  In: input32: pointer to a serialized xonly_pubkey (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_xonly_pubkey_parse(
+    const secp256k1_context* ctx,
+    secp256k1_xonly_pubkey* pubkey,
+    const unsigned char *input32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Serialize an xonly_pubkey object into a 32-byte sequence.
+ *
+ *  Returns: 1 always.
+ *
+ *  Args:     ctx: a secp256k1 context object (cannot be NULL).
+ *  Out: output32: a pointer to a 32-byte array to place the serialized key in
+ *                 (cannot be NULL).
+ *  In:    pubkey: a pointer to a secp256k1_xonly_pubkey containing an
+ *                 initialized public key (cannot be NULL).
+ */
+SECP256K1_API int secp256k1_xonly_pubkey_serialize(
+    const secp256k1_context* ctx,
+    unsigned char *output32,
+    const secp256k1_xonly_pubkey* pubkey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Converts a secp256k1_pubkey into a secp256k1_xonly_pubkey.
+ *
+ *  Returns: 1 if the public key was successfully converted
+ *           0 otherwise
+ *
+ *  Args:         ctx: pointer to a context object (cannot be NULL)
+ *  Out: xonly_pubkey: pointer to an x-only public key object for placing the
+ *                     converted public key (cannot be NULL)
+ *          pk_parity: pointer to an integer that will be set to 1 if the point
+ *                     encoded by xonly_pubkey is the negation of the pubkey and
+ *                     set to 0 otherwise. (can be NULL)
+ *  In:        pubkey: pointer to a public key that is converted (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_xonly_pubkey_from_pubkey(
+    const secp256k1_context* ctx,
+    secp256k1_xonly_pubkey *xonly_pubkey,
+    int *pk_parity,
+    const secp256k1_pubkey *pubkey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(4);
+
+/** Tweak an x-only public key by adding the generator multiplied with tweak32
+ *  to it.
+ *
+ *  Note that the resulting point can not in general be represented by an x-only
+ *  pubkey because it may have an odd Y coordinate. Instead, the output_pubkey
+ *  is a normal secp256k1_pubkey.
+ *
+ *  Returns: 0 if the arguments are invalid or the resulting public key would be
+ *           invalid (only when the tweak is the negation of the corresponding
+ *           secret key). 1 otherwise.
+ *
+ *  Args:           ctx: pointer to a context object initialized for verification
+ *                       (cannot be NULL)
+ *  Out:  output_pubkey: pointer to a public key to store the result. Will be set
+ *                       to an invalid value if this function returns 0 (cannot
+ *                       be NULL)
+ *  In: internal_pubkey: pointer to an x-only pubkey to apply the tweak to.
+ *                       (cannot be NULL).
+ *              tweak32: pointer to a 32-byte tweak. If the tweak is invalid
+ *                       according to secp256k1_ec_seckey_verify, this function
+ *                       returns 0. For uniformly random 32-byte arrays the
+ *                       chance of being invalid is negligible (around 1 in
+ *                       2^128) (cannot be NULL).
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_xonly_pubkey_tweak_add(
+    const secp256k1_context* ctx,
+    secp256k1_pubkey *output_pubkey,
+    const secp256k1_xonly_pubkey *internal_pubkey,
+    const unsigned char *tweak32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+/** Checks that a tweaked pubkey is the result of calling
+ *  secp256k1_xonly_pubkey_tweak_add with internal_pubkey and tweak32.
+ *
+ *  The tweaked pubkey is represented by its 32-byte x-only serialization and
+ *  its pk_parity, which can both be obtained by converting the result of
+ *  tweak_add to a secp256k1_xonly_pubkey.
+ *
+ *  Note that this alone does _not_ verify that the tweaked pubkey is a
+ *  commitment. If the tweak is not chosen in a specific way, the tweaked pubkey
+ *  can easily be the result of a different internal_pubkey and tweak.
+ *
+ *  Returns: 0 if the arguments are invalid or the tweaked pubkey is not the
+ *           result of tweaking the internal_pubkey with tweak32. 1 otherwise.
+ *  Args:            ctx: pointer to a context object initialized for verification
+ *                       (cannot be NULL)
+ *  In: tweaked_pubkey32: pointer to a serialized xonly_pubkey (cannot be NULL)
+ *     tweaked_pk_parity: the parity of the tweaked pubkey (whose serialization
+ *                        is passed in as tweaked_pubkey32). This must match the
+ *                        pk_parity value that is returned when calling
+ *                        secp256k1_xonly_pubkey with the tweaked pubkey, or
+ *                        this function will fail.
+ *       internal_pubkey: pointer to an x-only public key object to apply the
+ *                        tweak to (cannot be NULL)
+ *               tweak32: pointer to a 32-byte tweak (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_xonly_pubkey_tweak_add_check(
+    const secp256k1_context* ctx,
+    const unsigned char *tweaked_pubkey32,
+    int tweaked_pk_parity,
+    const secp256k1_xonly_pubkey *internal_pubkey,
+    const unsigned char *tweak32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);
+
+/** Compute the keypair for a secret key.
+ *
+ *  Returns: 1: secret was valid, keypair is ready to use
+ *           0: secret was invalid, try again with a different secret
+ *  Args:    ctx: pointer to a context object, initialized for signing (cannot be NULL)
+ *  Out: keypair: pointer to the created keypair (cannot be NULL)
+ *  In:   seckey: pointer to a 32-byte secret key (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_create(
+    const secp256k1_context* ctx,
+    secp256k1_keypair *keypair,
+    const unsigned char *seckey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Get the public key from a keypair.
+ *
+ *  Returns: 0 if the arguments are invalid. 1 otherwise.
+ *  Args:    ctx: pointer to a context object (cannot be NULL)
+ *  Out: pubkey: pointer to a pubkey object. If 1 is returned, it is set to
+ *               the keypair public key. If not, it's set to an invalid value.
+ *               (cannot be NULL)
+ *  In: keypair: pointer to a keypair (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_pub(
+    const secp256k1_context* ctx,
+    secp256k1_pubkey *pubkey,
+    const secp256k1_keypair *keypair
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Get the x-only public key from a keypair.
+ *
+ *  This is the same as calling secp256k1_keypair_pub and then
+ *  secp256k1_xonly_pubkey_from_pubkey.
+ *
+ *  Returns: 0 if the arguments are invalid. 1 otherwise.
+ *  Args:   ctx: pointer to a context object (cannot be NULL)
+ *  Out: pubkey: pointer to an xonly_pubkey object. If 1 is returned, it is set
+ *               to the keypair public key after converting it to an
+ *               xonly_pubkey. If not, it's set to an invalid value (cannot be
+ *               NULL).
+ *    pk_parity: pointer to an integer that will be set to the pk_parity
+ *               argument of secp256k1_xonly_pubkey_from_pubkey (can be NULL).
+ *  In: keypair: pointer to a keypair (cannot be NULL)
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_xonly_pub(
+    const secp256k1_context* ctx,
+    secp256k1_xonly_pubkey *pubkey,
+    int *pk_parity,
+    const secp256k1_keypair *keypair
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(4);
+
+/** Tweak a keypair by adding tweak32 to the secret key and updating the public
+ *  key accordingly.
+ *
+ *  Calling this function and then secp256k1_keypair_pub results in the same
+ *  public key as calling secp256k1_keypair_xonly_pub and then
+ *  secp256k1_xonly_pubkey_tweak_add.
+ *
+ *  Returns: 0 if the arguments are invalid or the resulting keypair would be
+ *           invalid (only when the tweak is the negation of the keypair's
+ *           secret key). 1 otherwise.
+ *
+ *  Args:       ctx: pointer to a context object initialized for verification
+ *                   (cannot be NULL)
+ *  In/Out: keypair: pointer to a keypair to apply the tweak to. Will be set to
+ *                   an invalid value if this function returns 0 (cannot be
+ *                   NULL).
+ *  In:     tweak32: pointer to a 32-byte tweak. If the tweak is invalid according
+ *                   to secp256k1_ec_seckey_verify, this function returns 0. For
+ *                   uniformly random 32-byte arrays the chance of being invalid
+ *                   is negligible (around 1 in 2^128) (cannot be NULL).
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_xonly_tweak_add(
+    const secp256k1_context* ctx,
+    secp256k1_keypair *keypair,
+    const unsigned char *tweak32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SECP256K1_EXTRAKEYS_H */