Add an api to get a pubkey and privkey from a privkey byte string.

ok and some tweaks from @jrick.

privkey.go

@@ -0,0 +1,28 @@
+// Copyright (c) 2013-2014 Conformal Systems LLC.
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package btcec
+
+import (
+	"crypto/ecdsa"
+	"math/big"
+)
+
+// PrivKeyFromBytes returns a private and public key for `curve' based on the
+// private key passed as an argument as a byte slice.
+func PrivKeyFromBytes(curve *KoblitzCurve, pk []byte) (*ecdsa.PrivateKey,
+	*PublicKey) {
+	x, y := curve.ScalarBaseMult(pk)
+
+	priv := &ecdsa.PrivateKey{
+		PublicKey: ecdsa.PublicKey{
+			Curve: curve,
+			X:     x,
+			Y:     y,
+		},
+		D: new(big.Int).SetBytes(pk),
+	}
+
+	return priv, (*PublicKey)(&priv.PublicKey)
+}

pubkey_test.go

@@ -6,7 +6,6 @@ package btcec_test
 
 import (
 	"bytes"
-	"crypto/ecdsa"
 	"github.com/conformal/btcec"
 	"github.com/davecgh/go-spew/spew"
 	"testing"
@@ -220,13 +219,10 @@ var pubKeyTests = []pubKeyTest{
 
 func TestPrivKeys(t *testing.T) {
 	for _, test := range privKeyTests {
-		x, y := btcec.S256().ScalarBaseMult(test.key)
+		_, pub := btcec.PrivKeyFromBytes(btcec.S256(), test.key)
-		pub := (*btcec.PublicKey)(&ecdsa.PublicKey{
+
-			Curve: btcec.S256(),
+		_, err := btcec.ParsePubKey(
-			X:     x,
+			pub.SerializeUncompressed(), btcec.S256())
-			Y:     y,
-		})
-		_, err := btcec.ParsePubKey(pub.SerializeUncompressed(), btcec.S256())
 		if err != nil {
 			t.Errorf("%s privkey: %v", test.name, err)
 			continue

signature_test.go

@@ -437,7 +437,7 @@ func testSignCompact(t *testing.T, tag string, curve *btcec.KoblitzCurve,
 
 	pk, wasCompressed, err := btcec.RecoverCompact(curve, sig, hashed)
 	if err != nil {
-		t.Errorf("%s: error recovering: %s", tag,  err)
+		t.Errorf("%s: error recovering: %s", tag, err)
 		return
 	}
 	if pk.X.Cmp(priv.X) != 0 || pk.Y.Cmp(priv.Y) != 0 {

test_coverage.txt

@@ -10,55 +10,56 @@ github.com/conformal/btcec/field.go	 fieldVal.PutBytes			 100.00% (32/32)
 github.com/conformal/btcec/btcec.go	 KoblitzCurve.addZ1EqualsZ2		 100.00% (30/30)
 github.com/conformal/btcec/btcec.go	 KoblitzCurve.addZ1AndZ2EqualsOne	 100.00% (29/29)
 github.com/conformal/btcec/btcec.go	 KoblitzCurve.addJacobian		 100.00% (22/22)
-github.com/conformal/btcec/btcec.go	 KoblitzCurve.doubleGeneric		 100.00% (18/18)
 github.com/conformal/btcec/btcec.go	 KoblitzCurve.doubleZ1EqualsOne		 100.00% (18/18)
+github.com/conformal/btcec/btcec.go	 KoblitzCurve.doubleGeneric		 100.00% (18/18)
 github.com/conformal/btcec/signature.go	 Signature.Serialize			 100.00% (13/13)
-github.com/conformal/btcec/btcec.go	 KoblitzCurve.fieldJacobianToBigAffine	 100.00% (12/12)
 github.com/conformal/btcec/field.go	 fieldVal.MulInt			 100.00% (12/12)
-github.com/conformal/btcec/field.go	 fieldVal.Add				 100.00% (11/11)
+github.com/conformal/btcec/btcec.go	 KoblitzCurve.fieldJacobianToBigAffine	 100.00% (12/12)
 github.com/conformal/btcec/field.go	 fieldVal.Add2				 100.00% (11/11)
-github.com/conformal/btcec/field.go	 fieldVal.SetBytes			 100.00% (11/11)
+github.com/conformal/btcec/field.go	 fieldVal.Add				 100.00% (11/11)
 github.com/conformal/btcec/field.go	 fieldVal.NegateVal			 100.00% (11/11)
-github.com/conformal/btcec/field.go	 fieldVal.Zero				 100.00% (10/10)
+github.com/conformal/btcec/field.go	 fieldVal.SetBytes			 100.00% (11/11)
-github.com/conformal/btcec/btcec.go	 KoblitzCurve.Add			 100.00% (10/10)
 github.com/conformal/btcec/btcec.go	 KoblitzCurve.ScalarMult		 100.00% (10/10)
+github.com/conformal/btcec/btcec.go	 KoblitzCurve.Add			 100.00% (10/10)
+github.com/conformal/btcec/field.go	 fieldVal.Zero				 100.00% (10/10)
 github.com/conformal/btcec/btcec.go	 KoblitzCurve.doubleJacobian		 100.00% (9/9)
 github.com/conformal/btcec/btcec.go	 initS256				 100.00% (9/9)
 github.com/conformal/btcec/pubkey.go	 PublicKey.SerializeHybrid		 100.00% (8/8)
 github.com/conformal/btcec/signature.go	 canonicalizeInt			 100.00% (8/8)
-github.com/conformal/btcec/pubkey.go	 PublicKey.SerializeCompressed		 100.00% (7/7)
 github.com/conformal/btcec/btcec.go	 KoblitzCurve.Double			 100.00% (7/7)
-github.com/conformal/btcec/pubkey.go	 PublicKey.SerializeUncompressed	 100.00% (5/5)
+github.com/conformal/btcec/pubkey.go	 PublicKey.SerializeCompressed		 100.00% (7/7)
-github.com/conformal/btcec/field.go	 fieldVal.SetByteSlice			 100.00% (5/5)
+github.com/conformal/btcec/privkey.go	 PrivKeyFromBytes			 100.00% (6/6)
 github.com/conformal/btcec/pubkey.go	 pad					 100.00% (5/5)
+github.com/conformal/btcec/field.go	 fieldVal.SetByteSlice			 100.00% (5/5)
+github.com/conformal/btcec/pubkey.go	 PublicKey.SerializeUncompressed	 100.00% (5/5)
+github.com/conformal/btcec/signature.go	 canonicalPadding			 100.00% (4/4)
 github.com/conformal/btcec/btcec.go	 KoblitzCurve.bigAffineToField		 100.00% (4/4)
 github.com/conformal/btcec/field.go	 fieldVal.SetHex			 100.00% (4/4)
-github.com/conformal/btcec/signature.go	 canonicalPadding			 100.00% (4/4)
 github.com/conformal/btcec/btcec.go	 KoblitzCurve.IsOnCurve			 100.00% (4/4)
 github.com/conformal/btcec/field.go	 fieldVal.SetInt			 100.00% (3/3)
 github.com/conformal/btcec/field.go	 fieldVal.Bytes				 100.00% (3/3)
-github.com/conformal/btcec/field.go	 fieldVal.IsZero			 100.00% (2/2)
-github.com/conformal/btcec/field.go	 fieldVal.AddInt			 100.00% (2/2)
-github.com/conformal/btcec/field.go	 fieldVal.Equals			 100.00% (2/2)
-github.com/conformal/btcec/field.go	 fieldVal.Set				 100.00% (2/2)
 github.com/conformal/btcec/field.go	 fieldVal.String			 100.00% (2/2)
+github.com/conformal/btcec/field.go	 fieldVal.Equals			 100.00% (2/2)
+github.com/conformal/btcec/field.go	 fieldVal.IsZero			 100.00% (2/2)
 github.com/conformal/btcec/btcec.go	 S256					 100.00% (2/2)
+github.com/conformal/btcec/field.go	 fieldVal.AddInt			 100.00% (2/2)
+github.com/conformal/btcec/field.go	 fieldVal.Set				 100.00% (2/2)
 github.com/conformal/btcec/pubkey.go	 isOdd					 100.00% (1/1)
+github.com/conformal/btcec/field.go	 fieldVal.Negate			 100.00% (1/1)
+github.com/conformal/btcec/btcec.go	 initAll				 100.00% (1/1)
+github.com/conformal/btcec/signature.go	 ParseSignature				 100.00% (1/1)
 github.com/conformal/btcec/signature.go	 ParseDERSignature			 100.00% (1/1)
-github.com/conformal/btcec/btcec.go	 KoblitzCurve.ScalarBaseMult		 100.00% (1/1)
 github.com/conformal/btcec/field.go	 fieldVal.Mul				 100.00% (1/1)
 github.com/conformal/btcec/btcec.go	 KoblitzCurve.Params			 100.00% (1/1)
 github.com/conformal/btcec/field.go	 fieldVal.Square			 100.00% (1/1)
-github.com/conformal/btcec/field.go	 fieldVal.Negate			 100.00% (1/1)
 github.com/conformal/btcec/field.go	 fieldVal.IsOdd				 100.00% (1/1)
-github.com/conformal/btcec/btcec.go	 initAll				 100.00% (1/1)
+github.com/conformal/btcec/btcec.go	 KoblitzCurve.ScalarBaseMult		 100.00% (1/1)
 github.com/conformal/btcec/btcec.go	 KoblitzCurve.QPlus1Div4		 100.00% (1/1)
-github.com/conformal/btcec/signature.go	 ParseSignature				 100.00% (1/1)
+github.com/conformal/btcec/pubkey.go	 ParsePubKey				 92.86% (26/28)
-github.com/conformal/btcec/pubkey.go	 ParsePubKey				 96.15% (25/26)
-github.com/conformal/btcec/signature.go	 SignCompact				 90.91% (20/22)
 github.com/conformal/btcec/pubkey.go	 decompressPoint			 88.89% (8/9)
 github.com/conformal/btcec/signature.go	 recoverKeyFromSignature		 86.96% (20/23)
+github.com/conformal/btcec/signature.go	 SignCompact				 86.36% (19/22)
 github.com/conformal/btcec/signature.go	 RecoverCompact				 77.78% (7/9)
 github.com/conformal/btcec/signature.go	 hashToInt				 77.78% (7/9)
-github.com/conformal/btcec		 -------------------------------------	 98.80% (903/914)
+github.com/conformal/btcec		 -------------------------------------	 98.59% (909/922)