Initial project import

tools/v/vlib/crypto/hkdf/example_test.v

@@ -0,0 +1,34 @@
+import crypto.hkdf
+import crypto.rand
+import crypto.sha256
+
+// Usage example that expands one master secret into three other
+// cryptographically secure keys.
+fn test_usage() {
+	// Underlying hash function for HMAC.
+	key_len := sha256.new().size()
+
+	// Cryptographically secure master secret.
+	secret := [u8(0x00), 0x01, 0x02, 0x03] // i.e. NOT this.
+
+	// Non-secret salt, optional (can be empty).
+	// Recommended: hash-length random value.
+	salt := rand.read(sha256.new().size())!
+
+	// Non-secret context info prefix, optional (can be empty).
+	info_prefix := 'hkdf example'
+
+	// Generate three derived keys.
+	mut keys := [][]u8{}
+	for i in 0 .. 3 {
+		info := '${info_prefix} key ${i + 1}'
+		keys << hkdf.key(sha256.new, secret, salt, info, key_len)!
+	}
+
+	for derived_key in keys {
+		assert derived_key != []u8{len: key_len}
+	}
+	assert keys[0] != keys[1]
+	assert keys[1] != keys[2]
+	assert keys[0] != keys[2]
+}