keys: simplify error handling for PublicKey() and associated

PublicKey() for PrivateKey now just can't fail and it makes no sense to return
an error from it. There is a lot of associated functionality for which this
also is true, so adjust it accordingly and simplify a lot of code.

pkg/core/account_state_test.go

@@ -19,9 +19,7 @@ func TestDecodeEncodeAccountState(t *testing.T) {
 		balances[randomUint256()] = util.Fixed8(int64(randomInt(1, 10000)))
 		k, err := keys.NewPrivateKey()
 		assert.Nil(t, err)
-		p, err := k.PublicKey()
-		assert.Nil(t, err)
-		votes[i] = p
+		votes[i] = k.PublicKey()
 	}
 
 	a := &AccountState{

pkg/crypto/keys/nep2.go

@@ -44,10 +44,7 @@ func NEP2ScryptParams() ScryptParams {
 // NEP2Encrypt encrypts a the PrivateKey using a given passphrase
 // under the NEP-2 standard.
 func NEP2Encrypt(priv *PrivateKey, passphrase string) (s string, err error) {
-	address, err := priv.Address()
-	if err != nil {
-		return s, err
-	}
+	address := priv.Address()
 
 	addrHash := hash.Checksum([]byte(address))
 	// Normalize the passphrase according to the NFC standard.
@@ -119,14 +116,11 @@ func NEP2Decrypt(key, passphrase string) (s string, err error) {
 		return s, errors.New("password mismatch")
 	}
 
-	return privKey.WIF()
+	return privKey.WIF(), nil
 }
 
 func compareAddressHash(priv *PrivateKey, inhash []byte) bool {
-	address, err := priv.Address()
-	if err != nil {
-		return false
-	}
+	address := priv.Address()
 	addrHash := hash.Checksum([]byte(address))
 	return bytes.Equal(addrHash, inhash)
 }

pkg/crypto/keys/nep2_test.go

@@ -31,12 +31,10 @@ func TestNEP2Decrypt(t *testing.T) {
 
 		assert.Equal(t, testCase.PrivateKey, privKey.String())
 
-		wif, err := privKey.WIF()
-		assert.Nil(t, err)
+		wif := privKey.WIF()
 		assert.Equal(t, testCase.Wif, wif)
 
-		address, err := privKey.Address()
-		assert.Nil(t, err)
+		address := privKey.Address()
 		assert.Equal(t, testCase.Address, address)
 	}
 }

pkg/crypto/keys/private_key.go

@@ -7,7 +7,6 @@ import (
 	"crypto/sha256"
 	"crypto/x509"
 	"encoding/hex"
-	"errors"
 	"fmt"
 	"math/big"
 
@@ -58,18 +57,15 @@ func NewPrivateKeyFromRawBytes(b []byte) (*PrivateKey, error) {
 }
 
 // PublicKey derives the public key from the private key.
-func (p *PrivateKey) PublicKey() (*PublicKey, error) {
+func (p *PrivateKey) PublicKey() *PublicKey {
 	var (
 		c = elliptic.P256()
 		q = new(big.Int).SetBytes(p.b)
 	)
 
 	x, y := c.ScalarBaseMult(q.Bytes())
-	if !c.IsOnCurve(x, y) {
-		return nil, errors.New("failed to derive public key using elliptic curve")
-	}
 
-	return &PublicKey{X: x, Y: y}, nil
+	return &PublicKey{X: x, Y: y}
 }
 
 // NewPrivateKeyFromWIF returns a NEO PrivateKey from the given
@@ -85,27 +81,27 @@ func NewPrivateKeyFromWIF(wif string) (*PrivateKey, error) {
 // WIF returns the (wallet import format) of the PrivateKey.
 // Good documentation about this process can be found here:
 // https://en.bitcoin.it/wiki/Wallet_import_format
-func (p *PrivateKey) WIF() (string, error) {
-	return WIFEncode(p.b, WIFVersion, true)
+func (p *PrivateKey) WIF() string {
+	w, err := WIFEncode(p.b, WIFVersion, true)
+	// The only way WIFEncode() can fail is if we're to give it a key of
+	// wrong size, but we have a proper key here, aren't we?
+	if err != nil {
+		panic(err)
+	}
+	return w
 }
 
 // Address derives the public NEO address that is coupled with the private key, and
 // returns it as a string.
-func (p *PrivateKey) Address() (string, error) {
-	pk, err := p.PublicKey()
-	if err != nil {
-		return "", err
-	}
-	return pk.Address(), nil
+func (p *PrivateKey) Address() string {
+	pk := p.PublicKey()
+	return pk.Address()
 }
 
 // Signature creates the signature using the private key.
-func (p *PrivateKey) Signature() ([]byte, error) {
-	pk, err := p.PublicKey()
-	if err != nil {
-		return nil, err
-	}
-	return pk.Signature(), nil
+func (p *PrivateKey) Signature() []byte {
+	pk := p.PublicKey()
+	return pk.Signature()
 }
 
 // Sign signs arbitrary length data using the private key.

pkg/crypto/keys/private_key_test.go

@@ -14,14 +14,12 @@ func TestPrivateKey(t *testing.T) {
 	for _, testCase := range keytestcases.Arr {
 		privKey, err := NewPrivateKeyFromHex(testCase.PrivateKey)
 		assert.Nil(t, err)
-		address, err := privKey.Address()
-		assert.Nil(t, err)
+		address := privKey.Address()
 		assert.Equal(t, testCase.Address, address)
 
-		wif, err := privKey.WIF()
-		assert.Nil(t, err)
+		wif := privKey.WIF()
 		assert.Equal(t, testCase.Wif, wif)
-		pubKey, _ := privKey.PublicKey()
+		pubKey := privKey.PublicKey()
 		assert.Equal(t, hex.EncodeToString(pubKey.Bytes()), testCase.PublicKey)
 	}
 }

pkg/crypto/keys/publickey_test.go

@@ -23,8 +23,7 @@ func TestEncodeDecodePublicKey(t *testing.T) {
 	for i := 0; i < 4; i++ {
 		k, err := NewPrivateKey()
 		assert.Nil(t, err)
-		p, err := k.PublicKey()
-		assert.Nil(t, err)
+		p := k.PublicKey()
 		buf := new(bytes.Buffer)
 		assert.Nil(t, p.EncodeBinary(buf))
 

pkg/crypto/keys/sign_verify_test.go

@@ -15,8 +15,7 @@ func TestPubKeyVerify(t *testing.T) {
 	assert.Nil(t, err)
 	signedData, err := privKey.Sign(data)
 	assert.Nil(t, err)
-	pubKey, err := privKey.PublicKey()
-	assert.Nil(t, err)
+	pubKey := privKey.PublicKey()
 	result := pubKey.Verify(signedData, hashedData.Bytes())
 	expected := true
 	assert.Equal(t, expected, result)
@@ -29,7 +28,7 @@ func TestWrongPubKey(t *testing.T) {
 	signedData, _ := privKey.Sign(sample)
 
 	secondPrivKey, _ := NewPrivateKey()
-	wrongPubKey, _ := secondPrivKey.PublicKey()
+	wrongPubKey := secondPrivKey.PublicKey()
 
 	actual := wrongPubKey.Verify(signedData, hashedData.Bytes())
 	expcted := false

pkg/crypto/keys/wif.go

@@ -92,7 +92,7 @@ func WIFDecode(wif string, version byte) (*WIF, error) {
 }
 
 // GetVerificationScript returns NEO VM bytecode with checksig command for the public key.
-func (wif WIF) GetVerificationScript() ([]byte, error) {
+func (wif WIF) GetVerificationScript() []byte {
 	const (
 		pushbytes33 = 0x21
 		checksig    = 0xac
@@ -101,11 +101,8 @@ func (wif WIF) GetVerificationScript() ([]byte, error) {
 		vScript []byte
 		pubkey *PublicKey
 	)
-	pubkey, err := wif.PrivateKey.PublicKey()
-	if err != nil {
-		return nil, err
-	}
+	pubkey = wif.PrivateKey.PublicKey()
 	vScript = append([]byte{pushbytes33}, pubkey.Bytes()...)
 	vScript = append(vScript, checksig)
-	return vScript, nil
+	return vScript
 }

pkg/rpc/txBuilder.go

@@ -25,9 +25,7 @@ func CreateRawContractTransaction(params ContractTxParams) (*transaction.Transac
 		wif, assetID, address, amount, balancer = params.wif, params.assetID, params.address, params.value, params.balancer
 	)
 
-	if fromAddress, err = wif.PrivateKey.Address(); err != nil {
-		return nil, errs.Wrapf(err, "Failed to take address from WIF: %v", wif.S)
-	}
+	fromAddress = wif.PrivateKey.Address()
 
 	if fromAddressHash, err = crypto.Uint160DecodeAddress(fromAddress); err != nil {
 		return nil, errs.Wrapf(err, "Failed to take script hash from address: %v", fromAddress)
@@ -59,9 +57,7 @@ func CreateRawContractTransaction(params ContractTxParams) (*transaction.Transac
 	if witness.InvocationScript, err = GetInvocationScript(tx, wif); err != nil {
 		return nil, errs.Wrap(err, "Failed to create invocation script")
 	}
-	if witness.VerificationScript, err = wif.GetVerificationScript(); err != nil {
-		return nil, errs.Wrap(err, "Failed to create verification script")
-	}
+	witness.VerificationScript = wif.GetVerificationScript()
 	tx.Scripts = append(tx.Scripts, &witness)
 	tx.Hash()
 

pkg/wallet/account.go

@@ -57,7 +57,7 @@ func NewAccount() (*Account, error) {
 	if err != nil {
 		return nil, err
 	}
-	return newAccountFromPrivateKey(priv)
+	return newAccountFromPrivateKey(priv), nil
 }
 
 // DecryptAccount decrypt the encryptedWIF with the given passphrase and
@@ -87,23 +87,14 @@ func NewAccountFromWIF(wif string) (*Account, error) {
 	if err != nil {
 		return nil, err
 	}
-	return newAccountFromPrivateKey(privKey)
+	return newAccountFromPrivateKey(privKey), nil
 }
 
 // newAccountFromPrivateKey created a wallet from the given PrivateKey.
-func newAccountFromPrivateKey(p *keys.PrivateKey) (*Account, error) {
-	pubKey, err := p.PublicKey()
-	if err != nil {
-		return nil, err
-	}
-	pubAddr, err := p.Address()
-	if err != nil {
-		return nil, err
-	}
-	wif, err := p.WIF()
-	if err != nil {
-		return nil, err
-	}
+func newAccountFromPrivateKey(p *keys.PrivateKey) *Account {
+	pubKey := p.PublicKey()
+	pubAddr := p.Address()
+	wif := p.WIF()
 
 	a := &Account{
 		publicKey:  pubKey.Bytes(),
@@ -112,5 +103,5 @@ func newAccountFromPrivateKey(p *keys.PrivateKey) (*Account, error) {
 		wif:        wif,
 	}
 
-	return a, nil
+	return a
 }