feat(crypto): CGo bridge smoke test — FastHash via Keccak-256

Verify CGo link to libcryptonote.a works with a known-vector hash test.

Co-Authored-By: Charon <charon@lethean.io>

crypto/crypto.go

@@ -0,0 +1,25 @@
+// SPDX-Licence-Identifier: EUPL-1.2
+
+package crypto
+
+/*
+#cgo CPPFLAGS: -I${SRCDIR}/upstream -I${SRCDIR}/compat
+#cgo LDFLAGS: -L${SRCDIR}/build -lcryptonote -lstdc++ -lssl -lcrypto
+#include "bridge.h"
+*/
+import "C"
+
+import "unsafe"
+
+// FastHash computes the CryptoNote fast hash (Keccak-256) of the input.
+func FastHash(data []byte) [32]byte {
+	var hash [32]byte
+	if len(data) == 0 {
+		C.bridge_fast_hash(nil, 0, (*C.uint8_t)(unsafe.Pointer(&hash[0])))
+	} else {
+		C.bridge_fast_hash((*C.uint8_t)(unsafe.Pointer(&data[0])),
+			C.size_t(len(data)),
+			(*C.uint8_t)(unsafe.Pointer(&hash[0])))
+	}
+	return hash
+}

crypto/crypto_test.go

@@ -0,0 +1,30 @@
+// SPDX-Licence-Identifier: EUPL-1.2
+
+package crypto_test
+
+import (
+	"encoding/hex"
+	"testing"
+
+	"forge.lthn.ai/core/go-blockchain/crypto"
+)
+
+func TestFastHash_Good_KnownVector(t *testing.T) {
+	// Empty input → known Keccak-256 hash.
+	input := []byte{}
+	expected := "c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470"
+
+	got := crypto.FastHash(input)
+	if hex.EncodeToString(got[:]) != expected {
+		t.Fatalf("FastHash(empty)\n  got:  %x\n  want: %s", got, expected)
+	}
+}
+
+func TestFastHash_Good_HelloWorld(t *testing.T) {
+	input := []byte("Hello, World!")
+	got := crypto.FastHash(input)
+	var zero [32]byte
+	if got == zero {
+		t.Fatal("FastHash returned zero hash")
+	}
+}

crypto/doc.go

@@ -0,0 +1,10 @@
+// SPDX-Licence-Identifier: EUPL-1.2
+
+// Package crypto provides CryptoNote cryptographic operations via CGo
+// bridge to the vendored upstream C++ library.
+//
+// Build the C++ library before running tests:
+//
+//	cmake -S crypto -B crypto/build -DCMAKE_BUILD_TYPE=Release
+//	cmake --build crypto/build --parallel
+package crypto