base58: move into its own package

It doesn't belong to crypto in any way other than it uses hash function
internally.

pkg/encoding/base58/base58_test.go

@@ -0,0 +1,32 @@
+package base58
+
+import (
+	"encoding/hex"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCheckEncodeDecode(t *testing.T) {
+	var b58CsumEncoded = "KxhEDBQyyEFymvfJD96q8stMbJMbZUb6D1PmXqBWZDU2WvbvVs9o"
+	var b58CsumDecodedHex = "802bfe58ab6d9fd575bdc3a624e4825dd2b375d64ac033fbc46ea79dbab4f69a3e01"
+
+	b58CsumDecoded, _ := hex.DecodeString(b58CsumDecodedHex)
+	encoded := CheckEncode(b58CsumDecoded)
+	decoded, err := CheckDecode(b58CsumEncoded)
+	assert.Nil(t, err)
+	assert.Equal(t, encoded, b58CsumEncoded)
+	assert.Equal(t, decoded, b58CsumDecoded)
+}
+
+func TestCheckDecodeFailures(t *testing.T) {
+	badbase58 := "BASE%*"
+	_, err := CheckDecode(badbase58)
+	assert.NotNil(t, err)
+	shortbase58 := "THqY"
+	_, err = CheckDecode(shortbase58)
+	assert.NotNil(t, err)
+	badcsum := "KxhEDBQyyEFymvfJD96q8stMbJMbZUb6D1PmXqBWZDU2WvbvVs9A"
+	_, err = CheckDecode(badcsum)
+	assert.NotNil(t, err)
+}