Use crypto/ed25519 from stdlib

With Go 1.14 out and the x/crypto/ed25519 wrapper not updated to
fallthrough to the stdlib implementation we've decided to drop Go
1.12 supprot and move to stdlib imports entirely.

Fixes #158

README.md

@@ -67,6 +67,8 @@ We would love contributes that fall under the 'Planned Features' and fixing any
 
 ### Using
 
+This library needs at least Go 1.13.
+
 #### Pion DTLS
 For a DTLS 1.2 Server that listens on 127.0.0.1:4444
 ```sh

config.go

@@ -3,12 +3,11 @@ package dtls
 import (
 	"context"
 	"crypto/ecdsa"
+	"crypto/ed25519"
 	"crypto/tls"
 	"crypto/x509"
 	"time"
 
-	"golang.org/x/crypto/ed25519"
-
 	"github.com/pion/logging"
 )
 

crypto.go

@@ -3,6 +3,7 @@ package dtls
 import (
 	"crypto"
 	"crypto/ecdsa"
+	"crypto/ed25519"
 	"crypto/rand"
 	"crypto/rsa"
 	"crypto/sha256"
@@ -11,8 +12,6 @@ import (
 	"encoding/binary"
 	"math/big"
 	"time"
-
-	"golang.org/x/crypto/ed25519"
 )
 
 type ecdsaSignature struct {

e2e/e2e_v113_test.go

@@ -4,13 +4,12 @@ package e2e
 
 import (
 	"context"
+	"crypto/ed25519"
 	"crypto/rand"
 	"crypto/tls"
 	"testing"
 	"time"
 
-	"golang.org/x/crypto/ed25519"
-
 	"github.com/pion/dtls/v2"
 	"github.com/pion/dtls/v2/pkg/crypto/selfsign"
 	"github.com/pion/transport/test"

pkg/crypto/selfsign/selfsign.go

@@ -4,6 +4,7 @@ package selfsign
 import (
 	"crypto"
 	"crypto/ecdsa"
+	"crypto/ed25519"
 	"crypto/elliptic"
 	"crypto/rand"
 	"crypto/tls"
@@ -13,8 +14,6 @@ import (
 	"errors"
 	"math/big"
 	"time"
-
-	"golang.org/x/crypto/ed25519"
 )
 
 var errInvalidPrivateKey = errors.New("selfsign: invalid private key type")

signature_hash_algorithm.go

@@ -3,10 +3,10 @@ package dtls
 import (
 	"crypto"
 	"crypto/ecdsa"
+	"crypto/ed25519"
 	"crypto/rsa"
 	"crypto/tls"
 
-	"golang.org/x/crypto/ed25519"
 	"golang.org/x/xerrors"
 )