Refactored into namespaced packages.

keys/keys.go

@@ -0,0 +1,34 @@
+package keys
+
+import (
+	"encoding/hex"
+	"git.wisehodl.dev/jay/go-roots/errors"
+	"github.com/decred/dcrd/dcrec/secp256k1/v4"
+)
+
+// GeneratePrivateKey generates a new, random secp256k1 private key and returns
+// it as a 64-character, lowercase hexadecimal string.
+func GeneratePrivateKey() (string, error) {
+	sk, err := secp256k1.GeneratePrivateKey()
+	if err != nil {
+		return "", err
+	}
+	skBytes := sk.Serialize()
+	return hex.EncodeToString(skBytes), nil
+}
+
+// GetPublicKey derives the public key from a private key hex string
+// and returns the x-coordinate as 64 lowercase hex characters.
+func GetPublicKey(privateKeyHex string) (string, error) {
+	if len(privateKeyHex) != 64 {
+		return "", errors.MalformedPrivKey
+	}
+	skBytes, err := hex.DecodeString(privateKeyHex)
+	if err != nil {
+		return "", errors.MalformedPrivKey
+	}
+
+	pk := secp256k1.PrivKeyFromBytes(skBytes).PubKey()
+	pkBytes := pk.SerializeCompressed()[1:]
+	return hex.EncodeToString(pkBytes), nil
+}

keys/keys_test.go

@@ -0,0 +1,39 @@
+package keys
+
+import (
+	"github.com/stretchr/testify/assert"
+	"regexp"
+	"testing"
+)
+
+const testSK = "f43a0435f69529f310bbd1d6263d2fbf0977f54bfe2310cc37ae5904b83bb167"
+const testPK = "cfa87f35acbde29ba1ab3ee42de527b2cad33ac487e80cf2d6405ea0042c8fef"
+
+var Hex64Pattern = regexp.MustCompile("^[a-f0-9]{64}$")
+
+func TestGeneratePrivateKey(t *testing.T) {
+	sk, err := GeneratePrivateKey()
+
+	assert.NoError(t, err)
+	if !Hex64Pattern.MatchString(sk) {
+		t.Errorf("invalid private key format: %s", sk)
+	}
+}
+
+func TestGenerateUniquePrivateKeys(t *testing.T) {
+	sk1, _ := GeneratePrivateKey()
+	sk2, _ := GeneratePrivateKey()
+	assert.NotEqual(t, sk1, sk2)
+}
+
+func TestGetPublicKey(t *testing.T) {
+	pk, err := GetPublicKey(testSK)
+
+	assert.NoError(t, err)
+	assert.Equal(t, testPK, pk)
+}
+
+func TestGetPublicKeyInvalidPrivateKey(t *testing.T) {
+	_, err := GetPublicKey("abc123")
+	assert.ErrorContains(t, err, "private key must be 64 lowercase hex characters")
+}