test: add Stellar crypto benchmarks and edge cases

test/chains/stellar/bench/crypto.bench.ts

@@ -0,0 +1,72 @@
+import { bench, describe } from 'vitest';
+import { ed25519 } from '@noble/curves/ed25519';
+import { sha256 } from '@noble/hashes/sha256';
+import { computeSharedSecret } from '../../../../src/chains/stellar/stealth';
+import { hashToScalar, deriveStealthPubKey } from '../../../../src/chains/stellar/scalar';
+
+const viewingKey = new Uint8Array(32).fill(0xaa);
+const viewingPubKey = ed25519.getPublicKey(viewingKey);
+
+const ephemeralKey = new Uint8Array(32).fill(0xbb);
+const ephemeralPubKey = ed25519.getPublicKey(ephemeralKey);
+
+const spendingPubKey = ed25519.getPublicKey(new Uint8Array(32).fill(0xcc));
+
+const sharedSecret = computeSharedSecret(viewingKey, ephemeralPubKey);
+const hashScalar = hashToScalar(sharedSecret);
+
+const BENCH_OPTIONS = {
+  time: 1,
+  iterations: 1,
+  warmupTime: 0,
+  warmupIterations: 0,
+};
+
+describe('Stellar crypto hot paths', () => {
+  bench(
+    'public view-tag SHA-256',
+    () => {
+      const input = new Uint8Array(
+        ephemeralPubKey.length + viewingPubKey.length,
+      );
+
+      input.set(ephemeralPubKey);
+      input.set(viewingPubKey, ephemeralPubKey.length);
+
+      sha256(input);
+    },
+    BENCH_OPTIONS,
+  );
+
+  bench(
+    'X25519 shared secret',
+    () => {
+      computeSharedSecret(viewingKey, ephemeralPubKey);
+    },
+    BENCH_OPTIONS,
+  );
+
+  bench(
+    'hash shared secret to scalar',
+    () => {
+      hashToScalar(sharedSecret);
+    },
+    BENCH_OPTIONS,
+  );
+
+  bench(
+    'Ed25519 BASE.multiply(hashScalar)',
+    () => {
+      ed25519.ExtendedPoint.BASE.multiply(hashScalar);
+    },
+    BENCH_OPTIONS,
+  );
+
+  bench(
+    'full stealth public-key derivation',
+    () => {
+      deriveStealthPubKey(spendingPubKey, hashScalar);
+    },
+    BENCH_OPTIONS,
+  );
+});

test/chains/stellar/properties.test.ts

@@ -131,7 +131,8 @@ describe('stealth pubkey correctness', () => {
       fc.property(scalarArb, scalarArb, (m, s) => {
         const sum = (m + s) % L;
 
-        const lhs = ed25519.ExtendedPoint.BASE.multiply(sum);
+        const lhs =
+          sum === 0n ? ed25519.ExtendedPoint.ZERO : ed25519.ExtendedPoint.BASE.multiply(sum);
 
         const rhs = ed25519.ExtendedPoint.BASE.multiply(m).add(
           ed25519.ExtendedPoint.BASE.multiply(s),
@@ -149,7 +150,12 @@ describe('stealth pubkey correctness', () => {
         const pub = ed25519.ExtendedPoint.BASE.multiply(m).toRawBytes();
         const derived = deriveStealthPubKey(pub, s);
 
-        const expected = ed25519.ExtendedPoint.BASE.multiply((m + s) % L).toRawBytes();
+        const sum = (m + s) % L;
+
+        const expectedPoint =
+          sum === 0n ? ed25519.ExtendedPoint.ZERO : ed25519.ExtendedPoint.BASE.multiply(sum);
+
+        const expected = expectedPoint.toRawBytes();
 
         expect(derived).toEqual(expected);
       }),