init

10 years ago · 6cf6981ed0
commit 6cf6981ed0
7 changed files with 1704 additions and 0 deletions
--- a/.gitignore
+++ b/.gitignore
@ -0,0 +1,24 @@
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe
+
+*~
--- a/28
+++ b/28
@ -0,0 +1,28 @@
+Copyright (c) 2013 Kyle Isom <kyle@tyrfingr.is>
+Copyright (c) 2012 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
--- a/94
+++ b/94
@ -0,0 +1,94 @@
+# NOTE
+
+This implementation is direct fork of Kylom's implementation. I claim no authorship over this code apart from some minor modifications.
+Please be aware this code **has not yet been reviewed**.
+
+ecies implements the Elliptic Curve Integrated Encryption Scheme.
+
+The package is designed to be compliant with the appropriate NIST
+standards, and therefore doesn't support the full SEC 1 algorithm set.
+
+
+STATUS:
+
+ecies should be ready for use. The ASN.1 support is only complete so
+far as to supported the listed algorithms before.
+
+
+CAVEATS
+
+1. CMAC support is currently not present.
+
+
+SUPPORTED ALGORITHMS
+
+        SYMMETRIC CIPHERS               HASH FUNCTIONS
+             AES128                         SHA-1
+             AES192                        SHA-224
+             AES256                        SHA-256
+                                           SHA-384
+        ELLIPTIC CURVE                     SHA-512
+             P256
+             P384		    KEY DERIVATION FUNCTION
+             P521	       NIST SP 800-65a Concatenation KDF
+
+Curve P224 isn't supported because it does not provide a minimum security
+level of AES128 with HMAC-SHA1. According to NIST SP 800-57, the security
+level of P224 is 112 bits of security. Symmetric ciphers use CTR-mode;
+message tags are computed using HMAC-<HASH> function.
+
+
+CURVE SELECTION
+
+According to NIST SP 800-57, the following curves should be selected:
+
+    +----------------+-------+
+    | SYMMETRIC SIZE | CURVE |
+    +----------------+-------+
+    |     128-bit    |  P256 |
+    +----------------+-------+
+    |     192-bit    |  P384 |
+    +----------------+-------+
+    |     256-bit    |  P521 |
+    +----------------+-------+
+
+
+TODO
+
+1. Look at serialising the parameters with the SEC 1 ASN.1 module.
+2. Validate ASN.1 formats with SEC 1.
+
+
+TEST VECTORS
+
+The only test vectors I've found so far date from 1993, predating AES
+and including only 163-bit curves. Therefore, there are no published
+test vectors to compare to.
+
+
+LICENSE
+
+ecies is released under the same license as the Go source code. See the
+LICENSE file for details.
+
+
+REFERENCES
+
+* SEC (Standard for Efficient Cryptography) 1, version 2.0: Elliptic
+  Curve Cryptography; Certicom, May 2009.
+  http://www.secg.org/download/aid-780/sec1-v2.pdf
+* GEC (Guidelines for Efficient Cryptography) 2, version 0.3: Test
+  Vectors for SEC 1; Certicom, September 1999.
+  http://www.secg.org/collateral/gec2.pdf
+* NIST SP 800-56a: Recommendation for Pair-Wise Key Establishment Schemes
+  Using Discrete Logarithm Cryptography. National Institute of Standards
+  and Technology, May 2007.
+  http://csrc.nist.gov/publications/nistpubs/800-56A/SP800-56A_Revision1_Mar08-2007.pdf
+* Suite B Implementer’s Guide to NIST SP 800-56A. National Security
+  Agency, July 28, 2009.
+  http://www.nsa.gov/ia/_files/SuiteB_Implementer_G-113808.pdf
+* NIST SP 800-57: Recommendation for Key Management – Part 1: General
+  (Revision 3). National Institute of Standards and Technology, July
+  2012.
+  http://csrc.nist.gov/publications/nistpubs/800-57/sp800-57_part1_rev3_general.pdf
+
--- a/asn1.go
+++ b/asn1.go
@ -0,0 +1,556 @@
+package ecies
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/elliptic"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"encoding/asn1"
+	"encoding/pem"
+	"fmt"
+	"hash"
+	"math/big"
+)
+
+var (
+	secgScheme     = []int{1, 3, 132, 1}
+	shaScheme      = []int{2, 16, 840, 1, 101, 3, 4, 2}
+	ansiX962Scheme = []int{1, 2, 840, 10045}
+	x963Scheme     = []int{1, 2, 840, 63, 0}
+)
+
+var ErrInvalidPrivateKey = fmt.Errorf("ecies: invalid private key")
+
+func doScheme(base, v []int) asn1.ObjectIdentifier {
+	var oidInts asn1.ObjectIdentifier
+	oidInts = append(oidInts, base...)
+	return append(oidInts, v...)
+}
+
+// curve OID code taken from crypto/x509, including
+//	- oidNameCurve*
+//	- namedCurveFromOID
+//	- oidFromNamedCurve
+// RFC 5480, 2.1.1.1. Named Curve
+//
+// secp224r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 33 }
+//
+// secp256r1 OBJECT IDENTIFIER ::= {
+//   iso(1) member-body(2) us(840) ansi-X9-62(10045) curves(3)
+//   prime(1) 7 }
+//
+// secp384r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 34 }
+//
+// secp521r1 OBJECT IDENTIFIER ::= {
+//   iso(1) identified-organization(3) certicom(132) curve(0) 35 }
+//
+// NB: secp256r1 is equivalent to prime256v1
+type secgNamedCurve asn1.ObjectIdentifier
+
+var (
+	secgNamedCurveP224 = secgNamedCurve{1, 3, 132, 0, 33}
+	secgNamedCurveP256 = secgNamedCurve{1, 2, 840, 10045, 3, 1, 7}
+	secgNamedCurveP384 = secgNamedCurve{1, 3, 132, 0, 34}
+	secgNamedCurveP521 = secgNamedCurve{1, 3, 132, 0, 35}
+	rawCurveP224       = []byte{6, 5, 4, 3, 1, 2, 9, 4, 0, 3, 3}
+	rawCurveP256       = []byte{6, 8, 4, 2, 1, 3, 4, 7, 2, 2, 0, 6, 6, 1, 3, 1, 7}
+	rawCurveP384       = []byte{6, 5, 4, 3, 1, 2, 9, 4, 0, 3, 4}
+	rawCurveP521       = []byte{6, 5, 4, 3, 1, 2, 9, 4, 0, 3, 5}
+)
+
+func rawCurve(curve elliptic.Curve) []byte {
+	switch curve {
+	case elliptic.P224():
+		return rawCurveP224
+	case elliptic.P256():
+		return rawCurveP256
+	case elliptic.P384():
+		return rawCurveP384
+	case elliptic.P521():
+		return rawCurveP521
+	default:
+		return nil
+	}
+}
+
+func (curve secgNamedCurve) Equal(curve2 secgNamedCurve) bool {
+	if len(curve) != len(curve2) {
+		return false
+	}
+	for i, _ := range curve {
+		if curve[i] != curve2[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func namedCurveFromOID(curve secgNamedCurve) elliptic.Curve {
+	switch {
+	case curve.Equal(secgNamedCurveP224):
+		return elliptic.P224()
+	case curve.Equal(secgNamedCurveP256):
+		return elliptic.P256()
+	case curve.Equal(secgNamedCurveP384):
+		return elliptic.P384()
+	case curve.Equal(secgNamedCurveP521):
+		return elliptic.P521()
+	}
+	return nil
+}
+
+func oidFromNamedCurve(curve elliptic.Curve) (secgNamedCurve, bool) {
+	switch curve {
+	case elliptic.P224():
+		return secgNamedCurveP224, true
+	case elliptic.P256():
+		return secgNamedCurveP256, true
+	case elliptic.P384():
+		return secgNamedCurveP384, true
+	case elliptic.P521():
+		return secgNamedCurveP521, true
+	}
+
+	return nil, false
+}
+
+// asnAlgorithmIdentifier represents the ASN.1 structure of the same name. See RFC
+// 5280, section 4.1.1.2.
+type asnAlgorithmIdentifier struct {
+	Algorithm  asn1.ObjectIdentifier
+	Parameters asn1.RawValue `asn1:"optional"`
+}
+
+func (a asnAlgorithmIdentifier) Cmp(b asnAlgorithmIdentifier) bool {
+	if len(a.Algorithm) != len(b.Algorithm) {
+		return false
+	}
+	for i, _ := range a.Algorithm {
+		if a.Algorithm[i] != b.Algorithm[i] {
+			return false
+		}
+	}
+	return true
+}
+
+type asnHashFunction asnAlgorithmIdentifier
+
+var (
+	oidSHA1   = asn1.ObjectIdentifier{1, 3, 14, 3, 2, 26}
+	oidSHA224 = doScheme(shaScheme, []int{4})
+	oidSHA256 = doScheme(shaScheme, []int{1})
+	oidSHA384 = doScheme(shaScheme, []int{2})
+	oidSHA512 = doScheme(shaScheme, []int{3})
+)
+
+func hashFromOID(oid asn1.ObjectIdentifier) func() hash.Hash {
+	switch {
+	case oid.Equal(oidSHA1):
+		return sha1.New
+	case oid.Equal(oidSHA224):
+		return sha256.New224
+	case oid.Equal(oidSHA256):
+		return sha256.New
+	case oid.Equal(oidSHA384):
+		return sha512.New384
+	case oid.Equal(oidSHA512):
+		return sha512.New
+	}
+	return nil
+}
+
+func oidFromHash(hash crypto.Hash) (asn1.ObjectIdentifier, bool) {
+	switch hash {
+	case crypto.SHA1:
+		return oidSHA1, true
+	case crypto.SHA224:
+		return oidSHA224, true
+	case crypto.SHA256:
+		return oidSHA256, true
+	case crypto.SHA384:
+		return oidSHA384, true
+	case crypto.SHA512:
+		return oidSHA512, true
+	default:
+		return nil, false
+	}
+}
+
+var (
+	asnAlgoSHA1 = asnHashFunction{
+		Algorithm: oidSHA1,
+	}
+	asnAlgoSHA224 = asnHashFunction{
+		Algorithm: oidSHA224,
+	}
+	asnAlgoSHA256 = asnHashFunction{
+		Algorithm: oidSHA256,
+	}
+	asnAlgoSHA384 = asnHashFunction{
+		Algorithm: oidSHA384,
+	}
+	asnAlgoSHA512 = asnHashFunction{
+		Algorithm: oidSHA512,
+	}
+)
+
+// type ASNasnSubjectPublicKeyInfo struct {
+//
+// }
+//
+
+type asnSubjectPublicKeyInfo struct {
+	Algorithm   asn1.ObjectIdentifier
+	PublicKey   asn1.BitString
+	Supplements ecpksSupplements `asn1:"optional"`
+}
+
+type asnECPKAlgorithms struct {
+	Type asn1.ObjectIdentifier
+}
+
+var idPublicKeyType = doScheme(ansiX962Scheme, []int{2})
+var idEcPublicKey = doScheme(idPublicKeyType, []int{1})
+var idEcPublicKeySupplemented = doScheme(idPublicKeyType, []int{0})
+
+func curveToRaw(curve elliptic.Curve) (rv asn1.RawValue, ok bool) {
+	switch curve {
+	case elliptic.P224(), elliptic.P256(), elliptic.P384(), elliptic.P521():
+		raw := rawCurve(curve)
+		return asn1.RawValue{
+			Tag:       30,
+			Bytes:     raw[2:],
+			FullBytes: raw,
+		}, true
+	default:
+		return rv, false
+	}
+}
+
+func asnECPublicKeyType(curve elliptic.Curve) (algo asnAlgorithmIdentifier, ok bool) {
+	raw, ok := curveToRaw(curve)
+	if !ok {
+		return
+	} else {
+		return asnAlgorithmIdentifier{Algorithm: idEcPublicKey,
+			Parameters: raw}, true
+	}
+}
+
+type asnECPrivKeyVer int
+
+var asnECPrivKeyVer1 asnECPrivKeyVer = 1
+
+type asnPrivateKey struct {
+	Version asnECPrivKeyVer
+	Private []byte
+	Curve   secgNamedCurve `asn1:"optional"`
+	Public  asn1.BitString
+}
+
+var asnECDH = doScheme(secgScheme, []int{12})
+
+type asnECDHAlgorithm asnAlgorithmIdentifier
+
+var (
+	dhSinglePass_stdDH_sha1kdf = asnECDHAlgorithm{
+		Algorithm: doScheme(x963Scheme, []int{2}),
+	}
+	dhSinglePass_stdDH_sha256kdf = asnECDHAlgorithm{
+		Algorithm: doScheme(secgScheme, []int{11, 1}),
+	}
+	dhSinglePass_stdDH_sha384kdf = asnECDHAlgorithm{
+		Algorithm: doScheme(secgScheme, []int{11, 2}),
+	}
+	dhSinglePass_stdDH_sha224kdf = asnECDHAlgorithm{
+		Algorithm: doScheme(secgScheme, []int{11, 0}),
+	}
+	dhSinglePass_stdDH_sha512kdf = asnECDHAlgorithm{
+		Algorithm: doScheme(secgScheme, []int{11, 3}),
+	}
+)
+
+func (a asnECDHAlgorithm) Cmp(b asnECDHAlgorithm) bool {
+	if len(a.Algorithm) != len(b.Algorithm) {
+		return false
+	}
+	for i, _ := range a.Algorithm {
+		if a.Algorithm[i] != b.Algorithm[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// asnNISTConcatenation is the only supported KDF at this time.
+type asnKeyDerivationFunction asnAlgorithmIdentifier
+
+var asnNISTConcatenationKDF = asnKeyDerivationFunction{
+	Algorithm: doScheme(secgScheme, []int{17, 1}),
+}
+
+func (a asnKeyDerivationFunction) Cmp(b asnKeyDerivationFunction) bool {
+	if len(a.Algorithm) != len(b.Algorithm) {
+		return false
+	}
+	for i, _ := range a.Algorithm {
+		if a.Algorithm[i] != b.Algorithm[i] {
+			return false
+		}
+	}
+	return true
+}
+
+var eciesRecommendedParameters = doScheme(secgScheme, []int{7})
+var eciesSpecifiedParameters = doScheme(secgScheme, []int{8})
+
+type asnECIESParameters struct {
+	KDF asnKeyDerivationFunction     `asn1:"optional"`
+	Sym asnSymmetricEncryption       `asn1:"optional"`
+	MAC asnMessageAuthenticationCode `asn1:"optional"`
+}
+
+type asnSymmetricEncryption asnAlgorithmIdentifier
+
+var (
+	aes128CTRinECIES = asnSymmetricEncryption{
+		Algorithm: doScheme(secgScheme, []int{21, 0}),
+	}
+	aes192CTRinECIES = asnSymmetricEncryption{
+		Algorithm: doScheme(secgScheme, []int{21, 1}),
+	}
+	aes256CTRinECIES = asnSymmetricEncryption{
+		Algorithm: doScheme(secgScheme, []int{21, 2}),
+	}
+)
+
+func (a asnSymmetricEncryption) Cmp(b asnSymmetricEncryption) bool {
+	if len(a.Algorithm) != len(b.Algorithm) {
+		return false
+	}
+	for i, _ := range a.Algorithm {
+		if a.Algorithm[i] != b.Algorithm[i] {
+			return false
+		}
+	}
+	return true
+}
+
+type asnMessageAuthenticationCode asnAlgorithmIdentifier
+
+var (
+	hmacFull = asnMessageAuthenticationCode{
+		Algorithm: doScheme(secgScheme, []int{22}),
+	}
+)
+
+func (a asnMessageAuthenticationCode) Cmp(b asnMessageAuthenticationCode) bool {
+	if len(a.Algorithm) != len(b.Algorithm) {
+		return false
+	}
+	for i, _ := range a.Algorithm {
+		if a.Algorithm[i] != b.Algorithm[i] {
+			return false
+		}
+	}
+	return true
+}
+
+type ecpksSupplements struct {
+	ECDomain      secgNamedCurve
+	ECCAlgorithms eccAlgorithmSet
+}
+
+type eccAlgorithmSet struct {
+	ECDH  asnECDHAlgorithm   `asn1:"optional"`
+	ECIES asnECIESParameters `asn1:"optional"`
+}
+
+func marshalSubjectPublicKeyInfo(pub *PublicKey) (subj asnSubjectPublicKeyInfo, err error) {
+	subj.Algorithm = idEcPublicKeySupplemented
+	curve, ok := oidFromNamedCurve(pub.Curve)
+	if !ok {
+		err = ErrInvalidPublicKey
+		return
+	}
+	subj.Supplements.ECDomain = curve
+	if pub.Params != nil {
+		subj.Supplements.ECCAlgorithms.ECDH = paramsToASNECDH(pub.Params)
+		subj.Supplements.ECCAlgorithms.ECIES = paramsToASNECIES(pub.Params)
+	}
+	pubkey := elliptic.Marshal(pub.Curve, pub.X, pub.Y)
+	subj.PublicKey = asn1.BitString{
+		BitLength: len(pubkey) * 8,
+		Bytes:     pubkey,
+	}
+	return
+}
+
+// Encode a public key to DER format.
+func MarshalPublic(pub *PublicKey) ([]byte, error) {
+	subj, err := marshalSubjectPublicKeyInfo(pub)
+	if err != nil {
+		return nil, err
+	}
+	return asn1.Marshal(subj)
+}
+
+// Decode a DER-encoded public key.
+func UnmarshalPublic(in []byte) (pub *PublicKey, err error) {
+	var subj asnSubjectPublicKeyInfo
+
+	if _, err = asn1.Unmarshal(in, &subj); err != nil {
+		return
+	}
+	if !subj.Algorithm.Equal(idEcPublicKeySupplemented) {
+		err = ErrInvalidPublicKey
+		return
+	}
+	pub = new(PublicKey)
+	pub.Curve = namedCurveFromOID(subj.Supplements.ECDomain)
+	x, y := elliptic.Unmarshal(pub.Curve, subj.PublicKey.Bytes)
+	if x == nil {
+		err = ErrInvalidPublicKey
+		return
+	}
+	pub.X = x
+	pub.Y = y
+	pub.Params = new(ECIESParams)
+	asnECIEStoParams(subj.Supplements.ECCAlgorithms.ECIES, pub.Params)
+	asnECDHtoParams(subj.Supplements.ECCAlgorithms.ECDH, pub.Params)
+	if pub.Params == nil {
+		if pub.Params = ParamsFromCurve(pub.Curve); pub.Params == nil {
+			err = ErrInvalidPublicKey
+		}
+	}
+	return
+}
+
+func marshalPrivateKey(prv *PrivateKey) (ecprv asnPrivateKey, err error) {
+	ecprv.Version = asnECPrivKeyVer1
+	ecprv.Private = prv.D.Bytes()
+
+	var ok bool
+	ecprv.Curve, ok = oidFromNamedCurve(prv.PublicKey.Curve)
+	if !ok {
+		err = ErrInvalidPrivateKey
+		return
+	}
+
+	var pub []byte
+	if pub, err = MarshalPublic(&prv.PublicKey); err != nil {
+		return
+	} else {
+		ecprv.Public = asn1.BitString{
+			BitLength: len(pub) * 8,
+			Bytes:     pub,
+		}
+	}
+	return
+}
+
+// Encode a private key to DER format.
+func MarshalPrivate(prv *PrivateKey) ([]byte, error) {
+	ecprv, err := marshalPrivateKey(prv)
+	if err != nil {
+		return nil, err
+	}
+	return asn1.Marshal(ecprv)
+}
+
+// Decode a private key from a DER-encoded format.
+func UnmarshalPrivate(in []byte) (prv *PrivateKey, err error) {
+	var ecprv asnPrivateKey
+
+	if _, err = asn1.Unmarshal(in, &ecprv); err != nil {
+		return
+	} else if ecprv.Version != asnECPrivKeyVer1 {
+		err = ErrInvalidPrivateKey
+		return
+	}
+
+	privateCurve := namedCurveFromOID(ecprv.Curve)
+	if privateCurve == nil {
+		err = ErrInvalidPrivateKey
+		return
+	}
+
+	prv = new(PrivateKey)
+	prv.D = new(big.Int).SetBytes(ecprv.Private)
+
+	if pub, err := UnmarshalPublic(ecprv.Public.Bytes); err != nil {
+		return nil, err
+	} else {
+		prv.PublicKey = *pub
+	}
+
+	return
+}
+
+// Export a public key to PEM format.
+func ExportPublicPEM(pub *PublicKey) (out []byte, err error) {
+	der, err := MarshalPublic(pub)
+	if err != nil {
+		return
+	}
+
+	var block pem.Block
+	block.Type = "ELLIPTIC CURVE PUBLIC KEY"
+	block.Bytes = der
+
+	buf := new(bytes.Buffer)
+	err = pem.Encode(buf, &block)
+	if err != nil {
+		return
+	} else {
+		out = buf.Bytes()
+	}
+	return
+}
+
+// Export a private key to PEM format.
+func ExportPrivatePEM(prv *PrivateKey) (out []byte, err error) {
+	der, err := MarshalPrivate(prv)
+	if err != nil {
+		return
+	}
+
+	var block pem.Block
+	block.Type = "ELLIPTIC CURVE PRIVATE KEY"
+	block.Bytes = der
+
+	buf := new(bytes.Buffer)
+	err = pem.Encode(buf, &block)
+	if err != nil {
+		return
+	} else {
+		out = buf.Bytes()
+	}
+	return
+}
+
+// Import a PEM-encoded public key.
+func ImportPublicPEM(in []byte) (pub *PublicKey, err error) {
+	p, _ := pem.Decode(in)
+	if p == nil || p.Type != "ELLIPTIC CURVE PUBLIC KEY" {
+		return nil, ErrInvalidPublicKey
+	}
+
+	pub, err = UnmarshalPublic(p.Bytes)
+	return
+}
+
+// Import a PEM-encoded private key.
+func ImportPrivatePEM(in []byte) (prv *PrivateKey, err error) {
+	p, _ := pem.Decode(in)
+	if p == nil || p.Type != "ELLIPTIC CURVE PRIVATE KEY" {
+		return nil, ErrInvalidPrivateKey
+	}
+
+	prv, err = UnmarshalPrivate(p.Bytes)
+	return
+}
--- a/ecies.go
+++ b/ecies.go
@ -0,0 +1,326 @@
+package ecies
+
+import (
+	"crypto/cipher"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/hmac"
+	"crypto/subtle"
+	"fmt"
+	"hash"
+	"io"
+	"math/big"
+)
+
+var (
+	ErrImport           = fmt.Errorf("ecies: failed to import key")
+	ErrInvalidCurve     = fmt.Errorf("ecies: invalid elliptic curve")
+	ErrInvalidParams    = fmt.Errorf("ecies: invalid ECIES parameters")
+	ErrInvalidPublicKey = fmt.Errorf("ecies: invalid public key")
+	ErrSharedKeyTooBig  = fmt.Errorf("ecies: shared key is too big")
+)
+
+// PublicKey is a representation of an elliptic curve public key.
+type PublicKey struct {
+	X *big.Int
+	Y *big.Int
+	elliptic.Curve
+	Params *ECIESParams
+}
+
+// Export an ECIES public key as an ECDSA public key.
+func (pub *PublicKey) ExportECDSA() *ecdsa.PublicKey {
+	return &ecdsa.PublicKey{pub.Curve, pub.X, pub.Y}
+}
+
+// Import an ECDSA public key as an ECIES public key.
+func ImportECDSAPublic(pub *ecdsa.PublicKey) *PublicKey {
+	return &PublicKey{
+		X:      pub.X,
+		Y:      pub.Y,
+		Curve:  pub.Curve,
+		Params: ParamsFromCurve(pub.Curve),
+	}
+}
+
+// PrivateKey is a representation of an elliptic curve private key.
+type PrivateKey struct {
+	PublicKey
+	D *big.Int
+}
+
+// Export an ECIES private key as an ECDSA private key.
+func (prv *PrivateKey) ExportECDSA() *ecdsa.PrivateKey {
+	pub := &prv.PublicKey
+	pubECDSA := pub.ExportECDSA()
+	return &ecdsa.PrivateKey{*pubECDSA, prv.D}
+}
+
+// Import an ECDSA private key as an ECIES private key.
+func ImportECDSA(prv *ecdsa.PrivateKey) *PrivateKey {
+	pub := ImportECDSAPublic(&prv.PublicKey)
+	return &PrivateKey{*pub, prv.D}
+}
+
+// Generate an elliptic curve public / private keypair. If params is nil,
+// the recommended default paramters for the key will be chosen.
+func GenerateKey(rand io.Reader, curve elliptic.Curve, params *ECIESParams) (prv *PrivateKey, err error) {
+	pb, x, y, err := elliptic.GenerateKey(curve, rand)
+	if err != nil {
+		return
+	}
+	prv = new(PrivateKey)
+	prv.PublicKey.X = x
+	prv.PublicKey.Y = y
+	prv.PublicKey.Curve = curve
+	prv.D = new(big.Int).SetBytes(pb)
+	if params == nil {
+		params = ParamsFromCurve(curve)
+	}
+	prv.PublicKey.Params = params
+	return
+}
+
+// MaxSharedKeyLength returns the maximum length of the shared key the
+// public key can produce.
+func MaxSharedKeyLength(pub *PublicKey) int {
+	return (pub.Curve.Params().BitSize + 7) / 8
+}
+
+// ECDH key agreement method used to establish secret keys for encryption.
+func (prv *PrivateKey) GenerateShared(pub *PublicKey, skLen, macLen int) (sk []byte, err error) {
+	if prv.PublicKey.Curve != pub.Curve {
+		err = ErrInvalidCurve
+		return
+	}
+	x, _ := pub.Curve.ScalarMult(pub.X, pub.Y, prv.D.Bytes())
+	if x == nil || (x.BitLen()+7)/8 < (skLen+macLen) {
+		err = ErrSharedKeyTooBig
+		return
+	}
+	sk = x.Bytes()[:skLen+macLen]
+	return
+}
+
+var (
+	ErrKeyDataTooLong = fmt.Errorf("ecies: can't supply requested key data")
+	ErrSharedTooLong  = fmt.Errorf("ecies: shared secret is too long")
+	ErrInvalidMessage = fmt.Errorf("ecies: invalid message")
+)
+
+var (
+	big2To32   = new(big.Int).Exp(big.NewInt(2), big.NewInt(32), nil)
+	big2To32M1 = new(big.Int).Sub(big2To32, big.NewInt(1))
+)
+
+func incCounter(ctr []byte) {
+	if ctr[3]++; ctr[3] != 0 {
+		return
+	} else if ctr[2]++; ctr[2] != 0 {
+		return
+	} else if ctr[1]++; ctr[1] != 0 {
+		return
+	} else if ctr[0]++; ctr[0] != 0 {
+		return
+	}
+	return
+}
+
+// NIST SP 800-56 Concatenation Key Derivation Function (see section 5.8.1).
+func concatKDF(hash hash.Hash, z, s1 []byte, kdLen int) (k []byte, err error) {
+	if s1 == nil {
+		s1 = make([]byte, 0)
+	}
+
+	reps := ((kdLen + 7) * 8) / (hash.BlockSize() * 8)
+	if big.NewInt(int64(reps)).Cmp(big2To32M1) > 0 {
+		fmt.Println(big2To32M1)
+		return nil, ErrKeyDataTooLong
+	}
+
+	counter := []byte{0, 0, 0, 1}
+	k = make([]byte, 0)
+
+	for i := 0; i <= reps; i++ {
+		hash.Write(counter)
+		hash.Write(z)
+		hash.Write(s1)
+		k = append(k, hash.Sum(nil)...)
+		hash.Reset()
+		incCounter(counter)
+	}
+
+	k = k[:kdLen]
+	return
+}
+
+// messageTag computes the MAC of a message (called the tag) as per
+// SEC 1, 3.5.
+func messageTag(hash func() hash.Hash, km, msg, shared []byte) []byte {
+	if shared == nil {
+		shared = make([]byte, 0)
+	}
+	mac := hmac.New(hash, km)
+	mac.Write(msg)
+	tag := mac.Sum(nil)
+	return tag
+}
+
+// Generate an initialisation vector for CTR mode.
+func generateIV(params *ECIESParams, rand io.Reader) (iv []byte, err error) {
+	iv = make([]byte, params.BlockSize)
+	_, err = io.ReadFull(rand, iv)
+	return
+}
+
+// symEncrypt carries out CTR encryption using the block cipher specified in the
+// parameters.
+func symEncrypt(rand io.Reader, params *ECIESParams, key, m []byte) (ct []byte, err error) {
+	c, err := params.Cipher(key)
+	if err != nil {
+		return
+	}
+
+	iv, err := generateIV(params, rand)
+	if err != nil {
+		return
+	}
+	ctr := cipher.NewCTR(c, iv)
+
+	ct = make([]byte, len(m)+params.BlockSize)
+	copy(ct, iv)
+	ctr.XORKeyStream(ct[params.BlockSize:], m)
+	return
+}
+
+// symDecrypt carries out CTR decryption using the block cipher specified in
+// the parameters
+func symDecrypt(rand io.Reader, params *ECIESParams, key, ct []byte) (m []byte, err error) {
+	c, err := params.Cipher(key)
+	if err != nil {
+		return
+	}
+
+	ctr := cipher.NewCTR(c, ct[:params.BlockSize])
+
+	m = make([]byte, len(ct)-params.BlockSize)
+	ctr.XORKeyStream(m, ct[params.BlockSize:])
+	return
+}
+
+// Encrypt encrypts a message using ECIES as specified in SEC 1, 5.1. If
+// the shared information parameters aren't being used, they should be
+// nil.
+func Encrypt(rand io.Reader, pub *PublicKey, m, s1, s2 []byte) (ct []byte, err error) {
+	params := pub.Params
+	if params == nil {
+		if params = ParamsFromCurve(pub.Curve); params == nil {
+			err = ErrUnsupportedECIESParameters
+			return
+		}
+	}
+	R, err := GenerateKey(rand, pub.Curve, params)
+	if err != nil {
+		return
+	}
+
+	hash := params.Hash()
+	z, err := R.GenerateShared(pub, params.KeyLen, params.KeyLen)
+	if err != nil {
+		return
+	}
+	K, err := concatKDF(hash, z, s1, params.KeyLen+params.KeyLen)
+	if err != nil {
+		return
+	}
+	Ke := K[:params.KeyLen]
+	Km := K[params.KeyLen:]
+	hash.Write(Km)
+	Km = hash.Sum(nil)
+	hash.Reset()
+
+	em, err := symEncrypt(rand, params, Ke, m)
+	if err != nil || len(em) <= params.BlockSize {
+		return
+	}
+
+	d := messageTag(params.Hash, Km, em, s2)
+
+	Rb := elliptic.Marshal(pub.Curve, R.PublicKey.X, R.PublicKey.Y)
+	ct = make([]byte, len(Rb)+len(em)+len(d))
+	copy(ct, Rb)
+	copy(ct[len(Rb):], em)
+	copy(ct[len(Rb)+len(em):], d)
+	return
+}
+
+// Decrypt decrypts an ECIES ciphertext.
+func (prv *PrivateKey) Decrypt(rand io.Reader, c, s1, s2 []byte) (m []byte, err error) {
+	if c == nil || len(c) == 0 {
+		err = ErrInvalidMessage
+		return
+	}
+	params := prv.PublicKey.Params
+	if params == nil {
+		if params = ParamsFromCurve(prv.PublicKey.Curve); params == nil {
+			err = ErrUnsupportedECIESParameters
+			return
+		}
+	}
+	hash := params.Hash()
+
+	var (
+		rLen   int
+		hLen   int = hash.Size()
+		mStart int
+		mEnd   int
+	)
+
+	switch c[0] {
+	case 2, 3, 4:
+		rLen = ((prv.PublicKey.Curve.Params().BitSize + 7) / 4)
+		if len(c) < (rLen + hLen + 1) {
+			err = ErrInvalidMessage
+			return
+		}
+	default:
+		err = ErrInvalidPublicKey
+		return
+	}
+
+	mStart = rLen
+	mEnd = len(c) - hLen
+
+	R := new(PublicKey)
+	R.Curve = prv.PublicKey.Curve
+	R.X, R.Y = elliptic.Unmarshal(R.Curve, c[:rLen])
+	if R.X == nil {
+		err = ErrInvalidPublicKey
+		return
+	}
+
+	z, err := prv.GenerateShared(R, params.KeyLen, params.KeyLen)
+	if err != nil {
+		return
+	}
+
+	K, err := concatKDF(hash, z, s1, params.KeyLen+params.KeyLen)
+	if err != nil {
+		return
+	}
+
+	Ke := K[:params.KeyLen]
+	Km := K[params.KeyLen:]
+	hash.Write(Km)
+	Km = hash.Sum(nil)
+	hash.Reset()
+
+	d := messageTag(params.Hash, Km, c[mStart:mEnd], s2)
+	if subtle.ConstantTimeCompare(c[mEnd:], d) != 1 {
+		err = ErrInvalidMessage
+		return
+	}
+
+	m, err = symDecrypt(rand, params, Ke, c[mStart:mEnd])
+	return
+}
--- a/ecies_test.go
+++ b/ecies_test.go
@ -0,0 +1,489 @@
+package ecies
+
+import (
+	"bytes"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/sha256"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"testing"
+)
+
+var dumpEnc bool
+
+func init() {
+	flDump := flag.Bool("dump", false, "write encrypted test message to file")
+	flag.Parse()
+	dumpEnc = *flDump
+}
+
+// Ensure the KDF generates appropriately sized keys.
+func TestKDF(t *testing.T) {
+	msg := []byte("Hello, world")
+	h := sha256.New()
+
+	k, err := concatKDF(h, msg, nil, 64)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+	if len(k) != 64 {
+		fmt.Printf("KDF: generated key is the wrong size (%d instead of 64\n",
+			len(k))
+		t.FailNow()
+	}
+}
+
+var skLen int
+var ErrBadSharedKeys = fmt.Errorf("ecies: shared keys don't match")
+
+// cmpParams compares a set of ECIES parameters. We assume, as per the
+// docs, that AES is the only supported symmetric encryption algorithm.
+func cmpParams(p1, p2 *ECIESParams) bool {
+	if p1.hashAlgo != p2.hashAlgo {
+		return false
+	} else if p1.KeyLen != p2.KeyLen {
+		return false
+	} else if p1.BlockSize != p2.BlockSize {
+		return false
+	}
+	return true
+}
+
+// cmpPublic returns true if the two public keys represent the same pojnt.
+func cmpPublic(pub1, pub2 PublicKey) bool {
+	if pub1.X == nil || pub1.Y == nil {
+		fmt.Println(ErrInvalidPublicKey.Error())
+		return false
+	}
+	if pub2.X == nil || pub2.Y == nil {
+		fmt.Println(ErrInvalidPublicKey.Error())
+		return false
+	}
+	pub1Out := elliptic.Marshal(pub1.Curve, pub1.X, pub1.Y)
+	pub2Out := elliptic.Marshal(pub2.Curve, pub2.X, pub2.Y)
+
+	return bytes.Equal(pub1Out, pub2Out)
+}
+
+// cmpPrivate returns true if the two private keys are the same.
+func cmpPrivate(prv1, prv2 *PrivateKey) bool {
+	if prv1 == nil || prv1.D == nil {
+		return false
+	} else if prv2 == nil || prv2.D == nil {
+		return false
+	} else if prv1.D.Cmp(prv2.D) != 0 {
+		return false
+	} else {
+		return cmpPublic(prv1.PublicKey, prv2.PublicKey)
+	}
+}
+
+// Validate the ECDH component.
+func TestSharedKey(t *testing.T) {
+	prv1, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+	skLen = MaxSharedKeyLength(&prv1.PublicKey) / 2
+
+	prv2, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	sk1, err := prv1.GenerateShared(&prv2.PublicKey, skLen, skLen)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	sk2, err := prv2.GenerateShared(&prv1.PublicKey, skLen, skLen)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	if !bytes.Equal(sk1, sk2) {
+		fmt.Println(ErrBadSharedKeys.Error())
+		t.FailNow()
+	}
+}
+
+// Verify that the key generation code fails when too much key data is
+// requested.
+func TestTooBigSharedKey(t *testing.T) {
+	prv1, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	prv2, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	_, err = prv1.GenerateShared(&prv2.PublicKey, skLen*2, skLen*2)
+	if err != ErrSharedKeyTooBig {
+		fmt.Println("ecdh: shared key should be too large for curve")
+		t.FailNow()
+	}
+
+	_, err = prv2.GenerateShared(&prv1.PublicKey, skLen*2, skLen*2)
+	if err != ErrSharedKeyTooBig {
+		fmt.Println("ecdh: shared key should be too large for curve")
+		t.FailNow()
+	}
+}
+
+// Ensure a public key can be successfully marshalled and unmarshalled, and
+// that the decoded key is the same as the original.
+func TestMarshalPublic(t *testing.T) {
+	prv, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	out, err := MarshalPublic(&prv.PublicKey)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	pub, err := UnmarshalPublic(out)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	if !cmpPublic(prv.PublicKey, *pub) {
+		fmt.Println("ecies: failed to unmarshal public key")
+		t.FailNow()
+	}
+}
+
+// Ensure that a private key can be encoded into DER format, and that
+// the resulting key is properly parsed back into a public key.
+func TestMarshalPrivate(t *testing.T) {
+	prv, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	out, err := MarshalPrivate(prv)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	if dumpEnc {
+		ioutil.WriteFile("test.out", out, 0644)
+	}
+
+	prv2, err := UnmarshalPrivate(out)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	if !cmpPrivate(prv, prv2) {
+		fmt.Println("ecdh: private key import failed")
+		t.FailNow()
+	}
+}
+
+// Ensure that a private key can be successfully encoded to PEM format, and
+// the resulting key is properly parsed back in.
+func TestPrivatePEM(t *testing.T) {
+	prv, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	out, err := ExportPrivatePEM(prv)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	if dumpEnc {
+		ioutil.WriteFile("test.key", out, 0644)
+	}
+
+	prv2, err := ImportPrivatePEM(out)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	} else if !cmpPrivate(prv, prv2) {
+		fmt.Println("ecdh: import from PEM failed")
+		t.FailNow()
+	}
+}
+
+// Ensure that a public key can be successfully encoded to PEM format, and
+// the resulting key is properly parsed back in.
+func TestPublicPEM(t *testing.T) {
+	prv, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	out, err := ExportPublicPEM(&prv.PublicKey)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	if dumpEnc {
+		ioutil.WriteFile("test.pem", out, 0644)
+	}
+
+	pub2, err := ImportPublicPEM(out)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	} else if !cmpPublic(prv.PublicKey, *pub2) {
+		fmt.Println("ecdh: import from PEM failed")
+		t.FailNow()
+	}
+}
+
+// Benchmark the generation of P256 keys.
+func BenchmarkGenerateKeyP256(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		if _, err := GenerateKey(rand.Reader, elliptic.P256(), nil); err != nil {
+			fmt.Println(err.Error())
+			b.FailNow()
+		}
+	}
+}
+
+// Benchmark the generation of P256 shared keys.
+func BenchmarkGenSharedKeyP256(b *testing.B) {
+	prv, err := GenerateKey(rand.Reader, elliptic.P256(), nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		b.FailNow()
+	}
+
+	for i := 0; i < b.N; i++ {
+		_, err := prv.GenerateShared(&prv.PublicKey, skLen, skLen)
+		if err != nil {
+			fmt.Println(err.Error())
+			b.FailNow()
+		}
+	}
+}
+
+// Verify that an encrypted message can be successfully decrypted.
+func TestEncryptDecrypt(t *testing.T) {
+	prv1, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	prv2, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	message := []byte("Hello, world.")
+	ct, err := Encrypt(rand.Reader, &prv2.PublicKey, message, nil, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	pt, err := prv2.Decrypt(rand.Reader, ct, nil, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	if !bytes.Equal(pt, message) {
+		fmt.Println("ecies: plaintext doesn't match message")
+		t.FailNow()
+	}
+
+	_, err = prv1.Decrypt(rand.Reader, ct, nil, nil)
+	if err == nil {
+		fmt.Println("ecies: encryption should not have succeeded")
+		t.FailNow()
+	}
+}
+
+// TestMarshalEncryption validates the encode/decode produces a valid
+// ECIES encryption key.
+func TestMarshalEncryption(t *testing.T) {
+	prv1, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	out, err := MarshalPrivate(prv1)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	prv2, err := UnmarshalPrivate(out)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	message := []byte("Hello, world.")
+	ct, err := Encrypt(rand.Reader, &prv2.PublicKey, message, nil, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	pt, err := prv2.Decrypt(rand.Reader, ct, nil, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	if !bytes.Equal(pt, message) {
+		fmt.Println("ecies: plaintext doesn't match message")
+		t.FailNow()
+	}
+
+	_, err = prv1.Decrypt(rand.Reader, ct, nil, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+}
+
+type testCase struct {
+	Curve    elliptic.Curve
+	Name     string
+	Expected bool
+}
+
+var testCases = []testCase{
+	testCase{
+		Curve:    elliptic.P224(),
+		Name:     "P224",
+		Expected: false,
+	},
+	testCase{
+		Curve:    elliptic.P256(),
+		Name:     "P256",
+		Expected: true,
+	},
+	testCase{
+		Curve:    elliptic.P384(),
+		Name:     "P384",
+		Expected: true,
+	},
+	testCase{
+		Curve:    elliptic.P521(),
+		Name:     "P521",
+		Expected: true,
+	},
+}
+
+// Test parameter selection for each curve, and that P224 fails automatic
+// parameter selection (see README for a discussion of P224). Ensures that
+// selecting a set of parameters automatically for the given curve works.
+func TestParamSelection(t *testing.T) {
+	for _, c := range testCases {
+		testParamSelection(t, c)
+	}
+}
+
+func testParamSelection(t *testing.T, c testCase) {
+	params := ParamsFromCurve(c.Curve)
+	if params == nil && c.Expected {
+		fmt.Printf("%s (%s)\n", ErrInvalidParams.Error(), c.Name)
+		t.FailNow()
+	} else if params != nil && !c.Expected {
+		fmt.Printf("ecies: parameters should be invalid (%s)\n",
+			c.Name)
+		t.FailNow()
+	}
+
+	prv1, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Printf("%s (%s)\n", err.Error(), c.Name)
+		t.FailNow()
+	}
+
+	prv2, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Printf("%s (%s)\n", err.Error(), c.Name)
+		t.FailNow()
+	}
+
+	message := []byte("Hello, world.")
+	ct, err := Encrypt(rand.Reader, &prv2.PublicKey, message, nil, nil)
+	if err != nil {
+		fmt.Printf("%s (%s)\n", err.Error(), c.Name)
+		t.FailNow()
+	}
+
+	pt, err := prv2.Decrypt(rand.Reader, ct, nil, nil)
+	if err != nil {
+		fmt.Printf("%s (%s)\n", err.Error(), c.Name)
+		t.FailNow()
+	}
+
+	if !bytes.Equal(pt, message) {
+		fmt.Printf("ecies: plaintext doesn't match message (%s)\n",
+			c.Name)
+		t.FailNow()
+	}
+
+	_, err = prv1.Decrypt(rand.Reader, ct, nil, nil)
+	if err == nil {
+		fmt.Printf("ecies: encryption should not have succeeded (%s)\n",
+			c.Name)
+		t.FailNow()
+	}
+
+}
+
+// Ensure that the basic public key validation in the decryption operation
+// works.
+func TestBasicKeyValidation(t *testing.T) {
+	badBytes := []byte{0, 1, 5, 6, 7, 8, 9}
+
+	prv, err := GenerateKey(rand.Reader, DefaultCurve, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	message := []byte("Hello, world.")
+	ct, err := Encrypt(rand.Reader, &prv.PublicKey, message, nil, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+		t.FailNow()
+	}
+
+	for _, b := range badBytes {
+		ct[0] = b
+		_, err := prv.Decrypt(rand.Reader, ct, nil, nil)
+		if err != ErrInvalidPublicKey {
+			fmt.Println("ecies: validated an invalid key")
+			t.FailNow()
+		}
+	}
+}
--- a/params.go
+++ b/params.go
@ -0,0 +1,187 @@
+package ecies
+
+// This file contains parameters for ECIES encryption, specifying the
+// symmetric encryption and HMAC parameters.
+
+import (
+	"crypto"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/elliptic"
+	"crypto/sha256"
+	"crypto/sha512"
+	"fmt"
+	"hash"
+)
+
+// The default curve for this package is the NIST P256 curve, which
+// provides security equivalent to AES-128.
+var DefaultCurve = elliptic.P256()
+
+var (
+	ErrUnsupportedECDHAlgorithm   = fmt.Errorf("ecies: unsupported ECDH algorithm")
+	ErrUnsupportedECIESParameters = fmt.Errorf("ecies: unsupported ECIES parameters")
+)
+
+type ECIESParams struct {
+	Hash      func() hash.Hash // hash function
+	hashAlgo  crypto.Hash
+	Cipher    func([]byte) (cipher.Block, error) // symmetric cipher
+	BlockSize int                                // block size of symmetric cipher
+	KeyLen    int                                // length of symmetric key
+}
+
+// Standard ECIES parameters:
+// * ECIES using AES128 and HMAC-SHA-256-16
+// * ECIES using AES256 and HMAC-SHA-256-32
+// * ECIES using AES256 and HMAC-SHA-384-48
+// * ECIES using AES256 and HMAC-SHA-512-64
+var (
+	ECIES_AES128_SHA256 *ECIESParams
+	ECIES_AES256_SHA256 *ECIESParams
+	ECIES_AES256_SHA384 *ECIESParams
+	ECIES_AES256_SHA512 *ECIESParams
+)
+
+func init() {
+	ECIES_AES128_SHA256 = &ECIESParams{
+		Hash:      sha256.New,
+		hashAlgo:  crypto.SHA256,
+		Cipher:    aes.NewCipher,
+		BlockSize: aes.BlockSize,
+		KeyLen:    16,
+	}
+
+	ECIES_AES256_SHA256 = &ECIESParams{
+		Hash:      sha256.New,
+		hashAlgo:  crypto.SHA256,
+		Cipher:    aes.NewCipher,
+		BlockSize: aes.BlockSize,
+		KeyLen:    32,
+	}
+
+	ECIES_AES256_SHA384 = &ECIESParams{
+		Hash:      sha512.New384,
+		hashAlgo:  crypto.SHA384,
+		Cipher:    aes.NewCipher,
+		BlockSize: aes.BlockSize,
+		KeyLen:    32,
+	}
+
+	ECIES_AES256_SHA512 = &ECIESParams{
+		Hash:      sha512.New,
+		hashAlgo:  crypto.SHA512,
+		Cipher:    aes.NewCipher,
+		BlockSize: aes.BlockSize,
+		KeyLen:    32,
+	}
+}
+
+var paramsFromCurve = map[elliptic.Curve]*ECIESParams{
+	elliptic.P256(): ECIES_AES128_SHA256,
+	elliptic.P384(): ECIES_AES256_SHA384,
+	elliptic.P521(): ECIES_AES256_SHA512,
+}
+
+func AddParamsForCurve(curve elliptic.Curve, params *ECIESParams) {
+	paramsFromCurve[curve] = params
+}
+
+// ParamsFromCurve selects parameters optimal for the selected elliptic curve.
+// Only the curves P256, P384, and P512 are supported.
+func ParamsFromCurve(curve elliptic.Curve) (params *ECIESParams) {
+	return paramsFromCurve[curve]
+
+	/*
+		switch curve {
+		case elliptic.P256():
+			return ECIES_AES128_SHA256
+		case elliptic.P384():
+			return ECIES_AES256_SHA384
+		case elliptic.P521():
+			return ECIES_AES256_SHA512
+		default:
+			return nil
+		}
+	*/
+}
+
+// ASN.1 encode the ECIES parameters relevant to the encryption operations.
+func paramsToASNECIES(params *ECIESParams) (asnParams asnECIESParameters) {
+	if nil == params {
+		return
+	}
+	asnParams.KDF = asnNISTConcatenationKDF
+	asnParams.MAC = hmacFull
+	switch params.KeyLen {
+	case 16:
+		asnParams.Sym = aes128CTRinECIES
+	case 24:
+		asnParams.Sym = aes192CTRinECIES
+	case 32:
+		asnParams.Sym = aes256CTRinECIES
+	}
+	return
+}
+
+// ASN.1 encode the ECIES parameters relevant to ECDH.
+func paramsToASNECDH(params *ECIESParams) (algo asnECDHAlgorithm) {
+	switch params.hashAlgo {
+	case crypto.SHA224:
+		algo = dhSinglePass_stdDH_sha224kdf
+	case crypto.SHA256:
+		algo = dhSinglePass_stdDH_sha256kdf
+	case crypto.SHA384:
+		algo = dhSinglePass_stdDH_sha384kdf
+	case crypto.SHA512:
+		algo = dhSinglePass_stdDH_sha512kdf
+	}
+	return
+}
+
+// ASN.1 decode the ECIES parameters relevant to the encryption stage.
+func asnECIEStoParams(asnParams asnECIESParameters, params *ECIESParams) {
+	if !asnParams.KDF.Cmp(asnNISTConcatenationKDF) {
+		params = nil
+		return
+	} else if !asnParams.MAC.Cmp(hmacFull) {
+		params = nil
+		return
+	}
+
+	switch {
+	case asnParams.Sym.Cmp(aes128CTRinECIES):
+		params.KeyLen = 16
+		params.BlockSize = 16
+		params.Cipher = aes.NewCipher
+	case asnParams.Sym.Cmp(aes192CTRinECIES):
+		params.KeyLen = 24
+		params.BlockSize = 16
+		params.Cipher = aes.NewCipher
+	case asnParams.Sym.Cmp(aes256CTRinECIES):
+		params.KeyLen = 32
+		params.BlockSize = 16
+		params.Cipher = aes.NewCipher
+	default:
+		params = nil
+	}
+}
+
+// ASN.1 decode the ECIES parameters relevant to ECDH.
+func asnECDHtoParams(asnParams asnECDHAlgorithm, params *ECIESParams) {
+	if asnParams.Cmp(dhSinglePass_stdDH_sha224kdf) {
+		params.hashAlgo = crypto.SHA224
+		params.Hash = sha256.New224
+	} else if asnParams.Cmp(dhSinglePass_stdDH_sha256kdf) {
+		params.hashAlgo = crypto.SHA256
+		params.Hash = sha256.New
+	} else if asnParams.Cmp(dhSinglePass_stdDH_sha384kdf) {
+		params.hashAlgo = crypto.SHA384
+		params.Hash = sha512.New384
+	} else if asnParams.Cmp(dhSinglePass_stdDH_sha512kdf) {
+		params.hashAlgo = crypto.SHA512
+		params.Hash = sha512.New
+	} else {
+		params = nil
+	}
+}