fix lint errors

internal/signature/ident.go

@@ -7,10 +7,11 @@ import (
 	"crypto/rand"
 	"crypto/rsa"
 	"crypto/sha256"
-	"crypto/x509"
-	"encoding/pem"
-	"fmt"
-	"os"
+_	"crypto/x509"
+_	"encoding/pem"
+_	"fmt"
+_	"os"
+	"errors"
 )
 
 var ErrInvalidSignature error = errors.New("Invalid signature")
@@ -31,7 +32,7 @@ func NewIdent() *Ident {
 func (i *Ident) Generate() error {
 	var err error
 	i.privateKey, err = rsa.GenerateKey(rand.Reader, 2048)
-	i.publicKey = &privateKey.PublicKey
+	i.publicKey = &i.privateKey.PublicKey
 	return err
 }
 
@@ -39,7 +40,7 @@ func (i *Ident) Sign(data []byte) ([]byte, error) {
 	checksum := sha256.Sum256(data)
 	sig, e := rsa.SignPKCS1v15(rand.Reader, i.privateKey, crypto.SHA256, checksum[:])
 	if e != nil {
-		return e
+		return nil, e
 	}
 	return sig, e
 }