Merge bitcoin-core/secp256k1#748: Add usage examples

7c9502c Add a copy of the CC0 license to the examples (Elichai Turkel)
42e0343 Add usage examples to the readme (Elichai Turkel)
517644e Optionally compile the examples in autotools, compile+run in travis (Elichai Turkel)
422a7cc Add a ecdh shared secret example (Elichai Turkel)
b0cfbcc Add a Schnorr signing and verifying example (Elichai Turkel)
fee7d4b Add an ECDSA signing and verifying example (Elichai Turkel)

Pull request description:

ACKs for top commit:
  real-or-random:
    ACK 7c9502c
  jonasnick:
    ACK 7c9502c

Tree-SHA512: c475cfd5b324b1e2d7126aa5bb1e7da25183b50adb7357d464c140de83d9097cb1bdc027d09aeadf167dbf9c8afd123235b0a1a742c5795089862418fafa1964

.cirrus.yml

@@ -23,6 +23,8 @@ env:
   BENCH: yes
   SECP256K1_BENCH_ITERS: 2
   CTIMETEST: yes
+  # Compile and run the tests
+  EXAMPLES: yes
 
 cat_logs_snippet: &CAT_LOGS
   always:

.gitignore

@@ -6,11 +6,16 @@ exhaustive_tests
 precompute_ecmult_gen
 precompute_ecmult
 valgrind_ctime_test
+ecdh_example
+ecdsa_example
+schnorr_example
 *.exe
 *.so
 *.a
 *.csv
 !.gitignore
+*.log
+*.trs
 
 Makefile
 configure

Makefile.am

@@ -63,6 +63,7 @@ noinst_HEADERS += contrib/lax_der_parsing.h
 noinst_HEADERS += contrib/lax_der_parsing.c
 noinst_HEADERS += contrib/lax_der_privatekey_parsing.h
 noinst_HEADERS += contrib/lax_der_privatekey_parsing.c
+noinst_HEADERS += examples/random.h
 
 PRECOMPUTED_LIB = libsecp256k1_precomputed.la
 noinst_LTLIBRARIES = $(PRECOMPUTED_LIB)
@@ -139,6 +140,40 @@ exhaustive_tests_LDFLAGS = -static
 TESTS += exhaustive_tests
 endif
 
+if USE_EXAMPLES
+noinst_PROGRAMS += ecdsa_example
+ecdsa_example_SOURCES = examples/ecdsa.c
+ecdsa_example_CPPFLAGS = -I$(top_srcdir)/include
+ecdsa_example_LDADD = libsecp256k1.la
+ecdsa_example_LDFLAGS = -static
+if BUILD_WINDOWS
+ecdsa_example_LDFLAGS += -lbcrypt
+endif
+TESTS += ecdsa_example
+if ENABLE_MODULE_ECDH
+noinst_PROGRAMS += ecdh_example
+ecdh_example_SOURCES = examples/ecdh.c
+ecdh_example_CPPFLAGS = -I$(top_srcdir)/include
+ecdh_example_LDADD = libsecp256k1.la
+ecdh_example_LDFLAGS = -static
+if BUILD_WINDOWS
+ecdh_example_LDFLAGS += -lbcrypt
+endif
+TESTS += ecdh_example
+endif
+if ENABLE_MODULE_SCHNORRSIG
+noinst_PROGRAMS += schnorr_example
+schnorr_example_SOURCES = examples/schnorr.c
+schnorr_example_CPPFLAGS = -I$(top_srcdir)/include
+schnorr_example_LDADD = libsecp256k1.la
+schnorr_example_LDFLAGS = -static
+if BUILD_WINDOWS
+schnorr_example_LDFLAGS += -lbcrypt
+endif
+TESTS += schnorr_example
+endif
+endif
+
 ### Precomputed tables
 EXTRA_PROGRAMS = precompute_ecmult precompute_ecmult_gen
 CLEANFILES = $(EXTRA_PROGRAMS)

README.md

@@ -69,6 +69,14 @@ libsecp256k1 is built using autotools:
     $ make check  # run the test suite
     $ sudo make install  # optional
 
+Usage examples
+-----------
+  Usage examples can be found in the [examples](examples) directory. To compile them you need to configure with `--enable-examples`.
+  For experimental modules, you will also need `--enable-experimental` as well as a flag for each individual module, e.g. `--enable-module-ecdh`.
+  * [ECDSA example](examples/ecdsa.c)
+  * [Schnorr Signatures example](examples/schnorr.c)
+  * [Deriving a shared secret(ECDH) example](examples/ecdh.c)
+
 Test coverage
 -----------
 

ci/cirrus.sh

@@ -19,6 +19,7 @@ valgrind --version || true
     --with-ecmult-gen-precision="$ECMULTGENPRECISION" \
     --enable-module-ecdh="$ECDH" --enable-module-recovery="$RECOVERY" \
     --enable-module-schnorrsig="$SCHNORRSIG" \
+    --enable-examples="$EXAMPLES" \
     --with-valgrind="$WITH_VALGRIND" \
     --host="$HOST" $EXTRAFLAGS
 

configure.ac

@@ -44,6 +44,8 @@ if test x"$ac_cv_prog_cc_c89" = x"no"; then
 fi
 AM_PROG_AS
 
+build_windows=no
+
 case $host_os in
   *darwin*)
      if  test x$cross_compiling != xyes; then
@@ -67,6 +69,9 @@ case $host_os in
        fi
      fi
    ;;
+   cygwin*|mingw*)
+     build_windows=yes
+   ;;
 esac
 
 # Try if some desirable compiler flags are supported and append them to SECP_CFLAGS.
@@ -134,6 +139,11 @@ AC_ARG_ENABLE(exhaustive_tests,
     [use_exhaustive_tests=$enableval],
     [use_exhaustive_tests=yes])
 
+AC_ARG_ENABLE(examples,
+    AS_HELP_STRING([--enable-examples],[compile the examples [default=no]]),
+    [use_examples=$enableval],
+    [use_examples=no])
+
 AC_ARG_ENABLE(module_ecdh,
     AS_HELP_STRING([--enable-module-ecdh],[enable ECDH shared secret computation]),
     [enable_module_ecdh=$enableval],
@@ -392,13 +402,15 @@ AC_SUBST(SECP_CFLAGS)
 AM_CONDITIONAL([ENABLE_COVERAGE], [test x"$enable_coverage" = x"yes"])
 AM_CONDITIONAL([USE_TESTS], [test x"$use_tests" != x"no"])
 AM_CONDITIONAL([USE_EXHAUSTIVE_TESTS], [test x"$use_exhaustive_tests" != x"no"])
+AM_CONDITIONAL([USE_EXAMPLES], [test x"$use_examples" != x"no"])
 AM_CONDITIONAL([USE_BENCHMARK], [test x"$use_benchmark" = x"yes"])
 AM_CONDITIONAL([ENABLE_MODULE_ECDH], [test x"$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"$set_asm" = x"arm"])
+AM_CONDITIONAL([BUILD_WINDOWS], [test "$build_windows" = "yes"])
 AC_SUBST(LIB_VERSION_CURRENT, _LIB_VERSION_CURRENT)
 AC_SUBST(LIB_VERSION_REVISION, _LIB_VERSION_REVISION)
 AC_SUBST(LIB_VERSION_AGE, _LIB_VERSION_AGE)
@@ -416,6 +428,7 @@ echo "  with external callbacks = $use_external_default_callbacks"
 echo "  with benchmarks         = $use_benchmark"
 echo "  with tests              = $use_tests"
 echo "  with coverage           = $enable_coverage"
+echo "  with examples           = $use_examples"
 echo "  module ecdh             = $enable_module_ecdh"
 echo "  module recovery         = $enable_module_recovery"
 echo "  module extrakeys        = $enable_module_extrakeys"

examples/EXAMPLES_COPYING

@@ -0,0 +1,121 @@
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