diff --git a/x/x.go b/x/x.go
new file mode 100644
index 0000000..4bbc852
--- /dev/null
+++ b/x/x.go
@@ -0,0 +1,144 @@
+// Package x provides experimental functionality.
+package x
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"math/big"
+
+	"github.com/pascaldekloe/jwt"
+)
+
+var encoding = base64.RawURLEncoding
+
+type jwk struct {
+	Keys []*jwk
+
+	Kty *string
+	Crv string
+
+	K, X, Y, N, E *string
+}
+
+// LoadJWK adds keys from a JWK or a JWK Set, and returns the count.
+// Both private and public keys can be used.
+func LoadJWK(keys *jwt.KeyRegister, data []byte) (n int, err error) {
+	j := new(jwk)
+	if err := json.Unmarshal(data, j); err != nil {
+		return 0, err
+	}
+
+	if j.Keys == nil {
+		// single key
+		if err := addJWK(keys, j); err != nil {
+			return 0, err
+		}
+		return 1, nil
+	}
+
+	// key set
+	for i, k := range j.Keys {
+		if err := addJWK(keys, k); err != nil {
+			return i, err
+		}
+	}
+	return len(j.Keys), nil
+}
+
+var (
+	errJWKNoKty = errors.New("jwt: JWK missing \"kty\" field")
+	errJWKParam = errors.New("jwt: JWK missing key–parameter field")
+
+	errJWKCurveSize = errors.New("jwt: JWK curve parameters don't match curve size")
+	errJWKCurveMiss = errors.New("jwt: JWK curve parameters are not on the curve")
+)
+
+func addJWK(keys *jwt.KeyRegister, j *jwk) error {
+	// See RFC 7518, subsection 6.1
+
+	if j.Kty == nil {
+		return errJWKNoKty
+	}
+	switch *j.Kty {
+	default:
+		return fmt.Errorf("jwt: JWK with unsupported key type %q", *j.Kty)
+
+	case "EC":
+		var curve elliptic.Curve
+		switch j.Crv {
+		case "P-256":
+			curve = elliptic.P256()
+		case "P-384":
+			curve = elliptic.P384()
+		case "P-521":
+			curve = elliptic.P521()
+		default:
+			return fmt.Errorf("jwt: JWK with unsupported elliptic curve %q", j.Crv)
+		}
+
+		x, err := keyParam(j.X)
+		if err != nil {
+			return err
+		}
+		y, err := keyParam(j.Y)
+		if err != nil {
+			return err
+		}
+
+		size := (curve.Params().BitSize + 7) / 8
+		xSize, ySize := (x.BitLen()+7)/8, (y.BitLen()+7)/8
+		if xSize != size || ySize != size {
+			return errJWKCurveSize
+		}
+
+		if !curve.IsOnCurve(x, y) {
+			return errJWKCurveMiss
+		}
+
+		keys.ECDSAs = append(keys.ECDSAs, &ecdsa.PublicKey{Curve: curve, X: x, Y: y})
+
+	case "RSA":
+		n, err := keyParam(j.N)
+		if err != nil {
+			return err
+		}
+		e, err := keyParam(j.E)
+		if err != nil {
+			return err
+		}
+
+		keys.RSAs = append(keys.RSAs, &rsa.PublicKey{N: n, E: int(e.Int64())})
+
+	case "oct":
+		if j.K == nil {
+			return errJWKParam
+		}
+
+		bytes, err := encoding.DecodeString(*j.K)
+		if err != nil {
+			return err
+		}
+
+		keys.Secrets = append(keys.Secrets, bytes)
+	}
+
+	return nil
+}
+
+func keyParam(p *string) (*big.Int, error) {
+	if p == nil {
+		return nil, errJWKParam
+	}
+
+	bytes, err := encoding.DecodeString(*p)
+	if err != nil {
+		return nil, fmt.Errorf("jwt: JWK with malformed key–parameter field: %s", err)
+	}
+
+	return new(big.Int).SetBytes(bytes), nil
+}
diff --git a/x/x_test.go b/x/x_test.go
new file mode 100644
index 0000000..4f90521
--- /dev/null
+++ b/x/x_test.go
@@ -0,0 +1,113 @@
+package x
+
+import (
+	"testing"
+
+	"github.com/pascaldekloe/jwt"
+)
+
+var GoldenJWKs = []struct {
+	Serial string
+}{
+	// RFC 7517, appendix A.1
+	{
+		Serial: `{
+			"keys": [{
+				"kty":"EC",
+				"crv":"P-256",
+				"x":"MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqv7D4",
+				"y":"4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM",
+				"use":"enc",
+				"kid":"1"
+			}, {
+				"kty":"RSA",
+				"n": "0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx4cbbfAAtVT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMstn64tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FDW2QvzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n91CbOpbISD08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINHaQ-G_xBniIqbw0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw",
+				"e":"AQAB",
+				"alg":"RS256",
+				"kid":"2011-04-29"
+			}]
+		}`,
+	},
+
+	// RFC 7517, appendix A.2
+	{
+		Serial: `{
+			"keys": [{
+				"kty":"EC",
+				"crv":"P-256",
+				"x":"MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqv7D4",
+				"y":"4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM",
+				"d":"870MB6gfuTJ4HtUnUvYMyJpr5eUZNP4Bk43bVdj3eAE",
+				"use":"enc",
+				"kid":"1"
+			}, {
+				"kty":"RSA",
+				"n":"0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx4cbbfAAtVT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMstn64tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FDW2QvzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n91CbOpbISD08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINHaQ-G_xBniIqbw0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw",
+				"e":"AQAB",
+				"d":"X4cTteJY_gn4FYPsXB8rdXix5vwsg1FLN5E3EaG6RJoVH-HLLKD9M7dx5oo7GURknchnrRweUkC7hT5fJLM0WbFAKNLWY2vv7B6NqXSzUvxT0_YSfqijwp3RTzlBaCxWp4doFk5N2o8Gy_nHNKroADIkJ46pRUohsXywbReAdYaMwFs9tv8d_cPVY3i07a3t8MN6TNwm0dSawm9v47UiCl3Sk5ZiG7xojPLu4sbg1U2jx4IBTNBznbJSzFHK66jT8bgkuqsk0GjskDJk19Z4qwjwbsnn4j2WBii3RL-Us2lGVkY8fkFzme1z0HbIkfz0Y6mqnOYtqc0X4jfcKoAC8Q",
+				"p":"83i-7IvMGXoMXCskv73TKr8637FiO7Z27zv8oj6pbWUQyLPQBQxtPVnwD20R-60eTDmD2ujnMt5PoqMrm8RfmNhVWDtjjMmCMjOpSXicFHj7XOuVIYQyqVWlWEh6dN36GVZYk93N8Bc9vY41xy8B9RzzOGVQzXvNEvn7O0nVbfs",
+				"q":"3dfOR9cuYq-0S-mkFLzgItgMEfFzB2q3hWehMuG0oCuqnb3vobLyumqjVZQO1dIrdwgTnCdpYzBcOfW5r370AFXjiWft_NGEiovonizhKpo9VVS78TzFgxkIdrecRezsZ-1kYd_s1qDbxtkDEgfAITAG9LUnADun4vIcb6yelxk",
+				"dp":"G4sPXkc6Ya9y8oJW9_ILj4xuppu0lzi_H7VTkS8xj5SdX3coE0oimYwxIi2emTAue0UOa5dpgFGyBJ4c8tQ2VF402XRugKDTP8akYhFo5tAA77Qe_NmtuYZc3C3m3I24G2GvR5sSDxUyAN2zq8Lfn9EUms6rY3Ob8YeiKkTiBj0",
+				"dq":"s9lAH9fggBsoFR8Oac2R_E2gw282rT2kGOAhvIllETE1efrA6huUUvMfBcMpn8lqeW6vzznYY5SSQF7pMdC_agI3nG8Ibp1BUb0JUiraRNqUfLhcQb_d9GF4Dh7e74WbRsobRonujTYN1xCaP6TO61jvWrX-L18txXw494Q_cgk",
+				"qi":"GyM_p6JrXySiz1toFgKbWV-JdI3jQ4ypu9rbMWx3rQJBfmt0FoYzgUIZEVFEcOqwemRN81zoDAaa-Bk0KWNGDjJHZDdDmFhW3AN7lI-puxk_mHZGJ11rxyR8O55XLSe3SPmRfKwZI6yU24ZxvQKFYItdldUKGzO6Ia6zTKhAVRU",
+				"alg":"RS256",
+				"kid":"2011-04-29"
+			}]
+		}`,
+	},
+
+	// RFC 7517, appendix A.3
+	{
+		Serial: `{
+			"keys": [{
+				"kty":"oct",
+				"alg":"A128KW",
+				"k":"GawgguFyGrWKav7AX4VKUg"
+			}, {
+				"kty":"oct",
+				"k":"AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow",
+				"kid":"HMAC key used in JWS spec Appendix A.1 example"
+			}]
+		}`,
+	},
+
+	// RFC 7517, appendix B
+	{
+		Serial: `{
+			"kty":"RSA",
+			"use":"sig",
+			"kid":"1b94c",
+			"n":"vrjOfz9Ccdgx5nQudyhdoR17V-IubWMeOZCwX_jj0hgAsz2J_pqYW08PLbK_PdiVGKPrqzmDIsLI7sA25VEnHU1uCLNwBuUiCO11_-7dYbsr4iJmG0Qu2j8DsVyT1azpJC_NG84Ty5KKthuCaPod7iI7w0LK9orSMhBEwwZDCxTWq4aYWAchc8t-emd9qOvWtVMDC2BXksRngh6X5bUYLy6AyHKvj-nUy1wgzjYQDwHMTplCoLtU-o-8SNnZ1tmRoGE9uJkBLdh5gFENabWnU5m1ZqZPdwS-qo-meMvVfJb6jJVWRpl2SUtCnYG2C32qvbWbjZ_jBPD5eunqsIo1vQ",
+			"e":"AQAB",
+			"x5c": ["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"]
+		}`,
+	},
+
+	// RFC 7517, appendix C
+	{
+		Serial: `{
+			"kty":"RSA",
+			"kid":"juliet@capulet.lit",
+			"use":"enc",
+			"n":"t6Q8PWSi1dkJj9hTP8hNYFlvadM7DflW9mWepOJhJ66w7nyoK1gPNqFMSQRyO125Gp-TEkodhWr0iujjHVx7BcV0llS4w5ACGgPrcAd6ZcSR0-Iqom-QFcNP8Sjg086MwoqQU_LYywlAGZ21WSdS_PERyGFiNnj3QQlO8Yns5jCtLCRwLHL0Pb1fEv45AuRIuUfVcPySBWYnDyGxvjYGDSM-AqWS9zIQ2ZilgT-GqUmipg0XOC0Cc20rgLe2ymLHjpHciCKVAbY5-L32-lSeZO-Os6U15_aXrk9Gw8cPUaX1_I8sLGuSiVdt3C_Fn2PZ3Z8i744FPFGGcG1qs2Wz-Q",
+			"e":"AQAB",
+			"d":"GRtbIQmhOZtyszfgKdg4u_N-R_mZGU_9k7JQ_jn1DnfTuMdSNprTeaSTyWfSNkuaAwnOEbIQVy1IQbWVV25NY3ybc_IhUJtfri7bAXYEReWaCl3hdlPKXy9UvqPYGR0kIXTQRqns-dVJ7jahlI7LyckrpTmrM8dWBo4_PMaenNnPiQgO0xnuToxutRZJfJvG4Ox4ka3GORQd9CsCZ2vsUDmsXOfUENOyMqADC6p1M3h33tsurY15k9qMSpG9OX_IJAXmxzAh_tWiZOwk2K4yxH9tS3Lq1yX8C1EWmeRDkK2ahecG85-oLKQt5VEpWHKmjOi_gJSdSgqcN96X52esAQ",
+			"p":"2rnSOV4hKSN8sS4CgcQHFbs08XboFDqKum3sc4h3GRxrTmQdl1ZK9uw-PIHfQP0FkxXVrx-WE-ZEbrqivH_2iCLUS7wAl6XvARt1KkIaUxPPSYB9yk31s0Q8UK96E3_OrADAYtAJs-M3JxCLfNgqh56HDnETTQhH3rCT5T3yJws",
+			"q":"1u_RiFDP7LBYh3N4GXLT9OpSKYP0uQZyiaZwBtOCBNJgQxaj10RWjsZu0c6Iedis4S7B_coSKB0Kj9PaPaBzg-IySRvvcQuPamQu66riMhjVtG6TlV8CLCYKrYl52ziqK0E_ym2QnkwsUX7eYTB7LbAHRK9GqocDE5B0f808I4s",
+			"dp":"KkMTWqBUefVwZ2_Dbj1pPQqyHSHjj90L5x_MOzqYAJMcLMZtbUtwKqvVDq3tbEo3ZIcohbDtt6SbfmWzggabpQxNxuBpoOOf_a_HgMXK_lhqigI4y_kqS1wY52IwjUn5rgRrJ-yYo1h41KR-vz2pYhEAeYrhttWtxVqLCRViD6c",
+			"dq":"AvfS0-gRxvn0bwJoMSnFxYcK1WnuEjQFluMGfwGitQBWtfZ1Er7t1xDkbN9GQTB9yqpDoYaN06H7CFtrkxhJIBQaj6nkF5KKS3TQtQ5qCzkOkmxIe3KRbBymXxkb5qwUpX5ELD5xFc6FeiafWYY63TmmEAu_lRFCOJ3xDea-ots",
+			"qi":"lSQi-w9CpyUReMErP1RsBLk7wNtOvs5EQpPqmuMvqW57NBUczScEoPwmUqqabu9V0-Py4dQ57_bapoKRu1R90bvuFnU63SHWEFglZQvJDMeAvmj4sm-Fp0oYu_neotgQ0hzbI5gry7ajdYy9-2lNx_76aBZoOUu9HCJ-UsfSOI8"
+		}`,
+	},
+}
+
+func Test(t *testing.T) {
+	for _, gold := range GoldenJWKs {
+		var keys jwt.KeyRegister
+		_, err := LoadJWK(&keys, []byte(gold.Serial))
+		if err != nil {
+			t.Errorf("got error %q for serial: %s", err, gold.Serial)
+			continue
+		}
+	}
+}