diff --git a/pkg/oidc/authorization.go b/pkg/oidc/authorization.go
index 6ad1016..a78d9dc 100644
--- a/pkg/oidc/authorization.go
+++ b/pkg/oidc/authorization.go
@@ -1,6 +1,7 @@
 package oidc
 
 import (
+	"encoding/json"
 	"errors"
 	"strings"
 	"time"
@@ -64,7 +65,7 @@ const (
 	PromptSelectAccount Prompt = "select_account"
 
 	//GrantTypeCode defines the grant_type `authorization_code` used for the Token Request in the Authorization Code Flow
-	GrantTypeCode   GrantType = "authorization_code"
+	GrantTypeCode GrantType = "authorization_code"
 	//GrantTypeBearer define the grant_type `urn:ietf:params:oauth:grant-type:jwt-bearer` used for the JWT Authorization Grant
 	GrantTypeBearer GrantType = "urn:ietf:params:oauth:grant-type:jwt-bearer"
 
@@ -148,10 +149,67 @@ type AccessTokenResponse struct {
 }
 
 type JWTTokenRequest struct {
-	Scopes    Scopes    `schema:"scope"`
-	Audience  []string  `schema:"aud"`
-	IssuedAt  time.Time `schema:"iat"`
-	ExpiresAt time.Time `schema:"exp"`
+	Issuer    string `json:"iss"`
+	Subject   string `json:"sub"`
+	Scopes    Scopes `json:"scope"`
+	Audience  string `json:"aud"`
+	IssuedAt  Time   `json:"iat"`
+	ExpiresAt Time   `json:"exp"`
+}
+
+func (j *JWTTokenRequest) GetClientID() string {
+	return j.Subject
+}
+
+func (j *JWTTokenRequest) GetSubject() string {
+	return j.Subject
+}
+
+func (j *JWTTokenRequest) GetScopes() []string {
+	return j.Scopes
+}
+
+type Time time.Time
+
+func (t *Time) UnmarshalJSON(data []byte) error {
+	var i int64
+	if err := json.Unmarshal(data, &i); err != nil {
+		return err
+	}
+	*t = Time(time.Unix(i, 0).UTC())
+	return nil
+}
+
+func (j *JWTTokenRequest) GetIssuer() string {
+	return j.Issuer
+}
+
+func (j *JWTTokenRequest) GetAudience() []string {
+	return []string{j.Audience}
+}
+
+func (j *JWTTokenRequest) GetExpiration() time.Time {
+	return time.Time(j.ExpiresAt)
+}
+
+func (j *JWTTokenRequest) GetIssuedAt() time.Time {
+	return time.Time(j.IssuedAt)
+}
+
+func (j *JWTTokenRequest) GetNonce() string {
+	return ""
+}
+
+func (j *JWTTokenRequest) GetAuthenticationContextClassReference() string {
+	return ""
+}
+
+func (j *JWTTokenRequest) GetAuthTime() time.Time {
+	return time.Time{}
+}
+
+func (j *JWTTokenRequest) GetAuthorizedParty() string {
+	return ""
 }
 
 type TokenExchangeRequest struct {
diff --git a/pkg/oidc/token.go b/pkg/oidc/token.go
index c468670..b06bc79 100644
--- a/pkg/oidc/token.go
+++ b/pkg/oidc/token.go
@@ -177,6 +177,42 @@ func (t *IDTokenClaims) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
+func (t *IDTokenClaims) GetIssuer() string {
+	return t.Issuer
+}
+
+func (t *IDTokenClaims) GetAudience() []string {
+	return t.Audiences
+}
+
+func (t *IDTokenClaims) GetExpiration() time.Time {
+	return t.Expiration
+}
+
+func (t *IDTokenClaims) GetIssuedAt() time.Time {
+	return t.IssuedAt
+}
+
+func (t *IDTokenClaims) GetNonce() string {
+	return t.Nonce
+}
+
+func (t *IDTokenClaims) GetAuthenticationContextClassReference() string {
+	return t.AuthenticationContextClassReference
+}
+
+func (t *IDTokenClaims) GetAuthTime() time.Time {
+	return t.AuthTime
+}
+
+func (t *IDTokenClaims) GetAuthorizedParty() string {
+	return t.AuthorizedParty
+}
+
+func (t *IDTokenClaims) SetSignature(alg jose.SignatureAlgorithm) {
+	t.Signature = alg
+}
+
 func (j *jsonToken) UnmarshalUserinfoProfile() UserinfoProfile {
 	locale, _ := language.Parse(j.Locale)
 	return UserinfoProfile{
diff --git a/pkg/oidc/verifier.go b/pkg/oidc/verifier.go
new file mode 100644
index 0000000..4b0f684
--- /dev/null
+++ b/pkg/oidc/verifier.go
@@ -0,0 +1,210 @@
+package oidc
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"gopkg.in/square/go-jose.v2"
+
+	"github.com/caos/oidc/pkg/utils"
+)
+
+type Claims interface {
+	GetIssuer() string
+	GetAudience() []string
+	GetExpiration() time.Time
+	GetIssuedAt() time.Time
+	GetNonce() string
+	GetAuthenticationContextClassReference() string
+	GetAuthTime() time.Time
+	GetAuthorizedParty() string
+	SetSignature(algorithm jose.SignatureAlgorithm)
+}
+
+var (
+	ErrParse         = errors.New("")
+	ErrIssuerInvalid = errors.New("issuer does not match")
+
+	ErrAudience = errors.New("audience is not valid")
+
+	ErrAzpMissing = errors.New("authorized party is not set. If Token is valid for multiple audiences, azp must not be empty")
+	ErrAzpInvalid = errors.New("authorized party is not valid")
+
+	ErrSignatureMissing        = errors.New("id_token does not contain a signature")
+	ErrSignatureMultiple       = errors.New("id_token contains multiple signatures")
+	ErrSignatureUnsupportedAlg = errors.New("signature algorithm not supported")
+	ErrSignatureInvalidPayload = errors.New("signature does not match Payload")
+
+	ErrExpired = errors.New("token has expired")
+
+	ErrIatInFuture = errors.New("issuedAt of token is in the future")
+
+	ErrIatToOld = errors.New("issuedAt of token is to old")
+	//
+	//ErrNonceInvalid = func(expected, actual string) *validationError {
+	//	return ValidationError("nonce does not match. Expected: %s, got: %s", expected, actual)
+	//}
+	ErrAcrInvalid         = errors.New("acr is invalid")
+	ErrAuthTimeNotPresent = errors.New("claim `auth_time` of token is missing")
+	ErrAuthTimeToOld      = errors.New("auth time of token is to old")
+
+	ErrAtHash = errors.New("at_hash does not correspond to access token")
+)
+
+//ACRVerifier specifies the function to be used by the `DefaultVerifier` for validating the acr claim
+type ACRVerifier func(string) error
+
+func DecryptToken(tokenString string) (string, error) {
+	return tokenString, nil //TODO: impl
+}
+
+func ParseToken(tokenString string, claims interface{}) ([]byte, error) {
+	parts := strings.Split(tokenString, ".")
+	if len(parts) != 3 {
+		return nil, fmt.Errorf("%w: token contains an invalid number of segments", ErrParse)
+	}
+	payload, err := base64.RawURLEncoding.DecodeString(parts[1])
+	if err != nil {
+		return nil, fmt.Errorf("%w: malformed jwt payload: %v", ErrParse, err)
+	}
+	err = json.Unmarshal(payload, claims)
+	return payload, err
+}
+
+type Verifier interface {
+	Issuer() string
+	ClientID() string
+	SupportedSignAlgs() []string
+	KeySet() KeySet
+	ACR() ACRVerifier
+	MaxAge() time.Duration
+	MaxAgeIAT() time.Duration
+	Offset() time.Duration
+}
+
+func CheckIssuer(issuer string, i Verifier) error {
+	if i.Issuer() != issuer {
+		return fmt.Errorf("%w: Expected: %s, got: %s", ErrIssuerInvalid, i.Issuer(), issuer)
+	}
+	return nil
+}
+
+func CheckAudience(audiences []string, i Verifier) error {
+	if !utils.Contains(audiences, i.ClientID()) {
+		return fmt.Errorf("%w: Audience must contain client_id (%s)", ErrAudience, i.ClientID())
+	}
+
+	//TODO: check aud trusted
+	return nil
+}
+
+//4. if multiple aud strings --> check if azp
+//5. if azp --> check azp == client_id
+func CheckAuthorizedParty(audiences []string, authorizedParty string, v Verifier) error {
+	if len(audiences) > 1 {
+		if authorizedParty == "" {
+			return ErrAzpMissing
+		}
+	}
+	if authorizedParty != "" && authorizedParty != v.ClientID() {
+		return fmt.Errorf("%w: azp %q must be equal to client_id %q", ErrAzpInvalid, authorizedParty, v.ClientID())
+	}
+	return nil
+}
+
+func CheckSignature(ctx context.Context, idTokenString string, payload []byte, claims Claims, v Verifier) error {
+	jws, err := jose.ParseSigned(idTokenString)
+	if err != nil {
+		return err
+	}
+	if len(jws.Signatures) == 0 {
+		return ErrSignatureMissing
+	}
+	if len(jws.Signatures) > 1 {
+		return ErrSignatureMultiple
+	}
+	sig := jws.Signatures[0]
+	supportedSigAlgs := v.SupportedSignAlgs()
+	if len(supportedSigAlgs) == 0 {
+		supportedSigAlgs = []string{"RS256"}
+	}
+	if !utils.Contains(supportedSigAlgs, sig.Header.Algorithm) {
+		return fmt.Errorf("%w: id token signed with unsupported algorithm, expected %q got %q", ErrSignatureUnsupportedAlg, supportedSigAlgs, sig.Header.Algorithm)
+	}
+
+	signedPayload, err := v.KeySet().VerifySignature(ctx, jws)
+	if err != nil {
+		return err
+	}
+
+	if !bytes.Equal(signedPayload, payload) {
+		return ErrSignatureInvalidPayload
+	}
+
+	claims.SetSignature(jose.SignatureAlgorithm(sig.Header.Algorithm))
+
+	return nil
+}
+
+func CheckExpiration(expiration time.Time, v Verifier) error {
+	expiration = expiration.Round(time.Second)
+	if !time.Now().UTC().Add(v.Offset()).Before(expiration) {
+		return ErrExpired
+	}
+	return nil
+}
+
+func CheckIssuedAt(issuedAt time.Time, v Verifier) error {
+	issuedAt = issuedAt.Round(time.Second)
+	offset := time.Now().UTC().Add(v.Offset()).Round(time.Second)
+	if issuedAt.After(offset) {
+		return fmt.Errorf("%w: (iat: %v, now with offset: %v)", ErrIatInFuture, issuedAt, offset)
+	}
+	if v.MaxAgeIAT() == 0 {
+		return nil
+	}
+	maxAge := time.Now().UTC().Add(-v.MaxAgeIAT()).Round(time.Second)
+	if issuedAt.Before(maxAge) {
+		return fmt.Errorf("%w: must not be older than %v, but was %v (%v to old)", ErrIatToOld, maxAge, issuedAt, maxAge.Sub(issuedAt))
+	}
+	return nil
+}
+
+/*
+func (v *DefaultVerifier) CheckNonce(nonce string) error {
+	if v.config.nonce == "" {
+		return nil
+	}
+	if v.config.nonce != nonce {
+		return ErrNonceInvalid(v.config.nonce, nonce)
+	}
+	return nil
+}*/
+func CheckAuthorizationContextClassReference(acr string, v Verifier) error {
+	if v.ACR() != nil {
+		if err := v.ACR()(acr); err != nil {
+			return fmt.Errorf("%w: %v", ErrAcrInvalid, err)
+		}
+	}
+	return nil
+}
+func CheckAuthTime(authTime time.Time, v Verifier) error {
+	if v.MaxAge() == 0 {
+		return nil
+	}
+	if authTime.IsZero() {
+		return ErrAuthTimeNotPresent
+	}
+	authTime = authTime.Round(time.Second)
+	maxAge := time.Now().UTC().Add(-v.MaxAge()).Round(time.Second)
+	if authTime.Before(maxAge) {
+		return fmt.Errorf("%w: must not be older than %v, but was %v (%v to old)", ErrAuthTimeToOld, maxAge, authTime, maxAge.Sub(authTime))
+	}
+	return nil
+}
diff --git a/pkg/op/default_op.go b/pkg/op/default_op.go
index 55d00fa..fbf34bc 100644
--- a/pkg/op/default_op.go
+++ b/pkg/op/default_op.go
@@ -275,7 +275,7 @@ func (p *DefaultOP) Crypto() Crypto {
 	return p.crypto
 }
 
-func (p *DefaultOP) Verifier() rp.Verifier {
+func (p *DefaultOP) ClientJWTVerifier() rp.Verifier {
 	return p.verifier
 }
 
diff --git a/pkg/op/discovery.go b/pkg/op/discovery.go
index 54c473b..5461cfa 100644
--- a/pkg/op/discovery.go
+++ b/pkg/op/discovery.go
@@ -7,6 +7,12 @@ import (
 	"github.com/caos/oidc/pkg/utils"
 )
 
+func DiscoveryHandler(c Configuration, s Signer) func(http.ResponseWriter, *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		Discover(w, CreateDiscoveryConfig(c, s))
+	}
+}
+
 func Discover(w http.ResponseWriter, config *oidc.DiscoveryConfiguration) {
 	utils.MarshalJSON(w, config)
 }
diff --git a/pkg/op/mock/storage.mock.go b/pkg/op/mock/storage.mock.go
index 9432616..83ef5ab 100644
--- a/pkg/op/mock/storage.mock.go
+++ b/pkg/op/mock/storage.mock.go
@@ -97,7 +97,7 @@ func (mr *MockStorageMockRecorder) CreateAuthRequest(arg0, arg1, arg2 interface{
 }
 
 // CreateToken mocks base method
-func (m *MockStorage) CreateToken(arg0 context.Context, arg1 op.AuthRequest) (string, time.Time, error) {
+func (m *MockStorage) CreateToken(arg0 context.Context, arg1 op.TokenRequest) (string, time.Time, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "CreateToken", arg0, arg1)
 	ret0, _ := ret[0].(string)
diff --git a/pkg/op/op.go b/pkg/op/op.go
index 624a8a1..eaba685 100644
--- a/pkg/op/op.go
+++ b/pkg/op/op.go
@@ -22,9 +22,12 @@ type OpenIDProvider interface {
 	HandleAuthorizeCallback(w http.ResponseWriter, r *http.Request)
 	HandleExchange(w http.ResponseWriter, r *http.Request)
 	HandleUserinfo(w http.ResponseWriter, r *http.Request)
-	HandleEndSession(w http.ResponseWriter, r *http.Request)
+	//HandleEndSession(w http.ResponseWriter, r *http.Request)
 	HandleKeys(w http.ResponseWriter, r *http.Request)
 	HttpHandler() http.Handler
+	SessionEnder
+	Signer() Signer
+	Probes() []ProbesFn
 }
 
 type HttpInterceptor func(http.Handler) http.Handler
@@ -42,13 +45,13 @@ func CreateRouter(o OpenIDProvider, interceptors ...HttpInterceptor) *mux.Router
 		handlers.AllowedOriginValidator(allowAllOrigins),
 	))
 	router.HandleFunc(healthzEndpoint, Healthz)
-	router.HandleFunc(readinessEndpoint, o.HandleReady)
-	router.HandleFunc(oidc.DiscoveryEndpoint, o.HandleDiscovery)
+	router.HandleFunc(readinessEndpoint, Ready(o.Probes()))
+	router.HandleFunc(oidc.DiscoveryEndpoint, DiscoveryHandler(o, o.Signer()))
 	router.Handle(o.AuthorizationEndpoint().Relative(), intercept(o.HandleAuthorize))
 	router.Handle(o.AuthorizationEndpoint().Relative()+"/{id}", intercept(o.HandleAuthorizeCallback))
 	router.Handle(o.TokenEndpoint().Relative(), intercept(o.HandleExchange))
 	router.HandleFunc(o.UserinfoEndpoint().Relative(), o.HandleUserinfo)
-	router.Handle(o.EndSessionEndpoint().Relative(), intercept(o.HandleEndSession))
+	router.Handle(o.EndSessionEndpoint().Relative(), intercept(EndSessionHandler(o)))
 	router.HandleFunc(o.KeysEndpoint().Relative(), o.HandleKeys)
 	return router
 }
diff --git a/pkg/op/probes.go b/pkg/op/probes.go
index 50e8a0f..ab12851 100644
--- a/pkg/op/probes.go
+++ b/pkg/op/probes.go
@@ -14,6 +14,12 @@ func Healthz(w http.ResponseWriter, r *http.Request) {
 	ok(w)
 }
 
+func Ready(probes []ProbesFn) func(w http.ResponseWriter, r *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		Readiness(w, r, probes...)
+	}
+}
+
 func Readiness(w http.ResponseWriter, r *http.Request, probes ...ProbesFn) {
 	ctx := r.Context()
 	for _, probe := range probes {
diff --git a/pkg/op/session.go b/pkg/op/session.go
index e60f71b..30dd5ea 100644
--- a/pkg/op/session.go
+++ b/pkg/op/session.go
@@ -16,6 +16,12 @@ type SessionEnder interface {
 	DefaultLogoutRedirectURI() string
 }
 
+func EndSessionHandler(ender SessionEnder) func(http.ResponseWriter, *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		EndSession(w, r, ender)
+	}
+}
+
 func EndSession(w http.ResponseWriter, r *http.Request, ender SessionEnder) {
 	req, err := ParseEndSessionRequest(r, ender.Decoder())
 	if err != nil {
diff --git a/pkg/op/storage.go b/pkg/op/storage.go
index 17023c1..0eee936 100644
--- a/pkg/op/storage.go
+++ b/pkg/op/storage.go
@@ -16,7 +16,7 @@ type AuthStorage interface {
 	SaveAuthCode(context.Context, string, string) error
 	DeleteAuthRequest(context.Context, string) error
 
-	CreateToken(context.Context, AuthRequest) (string, time.Time, error)
+	CreateToken(context.Context, TokenRequest) (string, time.Time, error)
 
 	TerminateSession(context.Context, string, string) error
 
diff --git a/pkg/op/token.go b/pkg/op/token.go
index 0fbcf60..10c8519 100644
--- a/pkg/op/token.go
+++ b/pkg/op/token.go
@@ -14,12 +14,19 @@ type TokenCreator interface {
 	Crypto() Crypto
 }
 
+type TokenRequest interface {
+	GetClientID() string
+	GetSubject() string
+	GetAudience() []string
+	GetScopes() []string
+}
+
 func CreateTokenResponse(ctx context.Context, authReq AuthRequest, client Client, creator TokenCreator, createAccessToken bool, code string) (*oidc.AccessTokenResponse, error) {
 	var accessToken string
 	var validity time.Duration
 	if createAccessToken {
 		var err error
-		accessToken, validity, err = CreateAccessToken(ctx, authReq, client, creator)
+		accessToken, validity, err = CreateAccessToken(ctx, authReq, client.AccessTokenType(), creator)
 		if err != nil {
 			return nil, err
 		}
@@ -43,8 +50,8 @@ func CreateTokenResponse(ctx context.Context, authReq AuthRequest, client Client
 	}, nil
 }
 
-func CreateJWTTokenResponse(ctx context.Context, authReq AuthRequest, client Client, creator TokenCreator) (*oidc.AccessTokenResponse, error) {
-	accessToken, validity, err := CreateAccessToken(ctx, authReq, client, creator)
+func CreateJWTTokenResponse(ctx context.Context, tokenRequest TokenRequest, creator TokenCreator) (*oidc.AccessTokenResponse, error) {
+	accessToken, validity, err := CreateAccessToken(ctx, tokenRequest, AccessTokenTypeBearer, creator)
 	if err != nil {
 		return nil, err
 	}
@@ -57,13 +64,13 @@ func CreateJWTTokenResponse(ctx context.Context, authReq AuthRequest, client Cli
 	}, nil
 }
 
-func CreateAccessToken(ctx context.Context, authReq AuthRequest, client Client, creator TokenCreator) (token string, validity time.Duration, err error) {
+func CreateAccessToken(ctx context.Context, authReq TokenRequest, accessTokenType AccessTokenType, creator TokenCreator) (token string, validity time.Duration, err error) {
 	id, exp, err := creator.Storage().CreateToken(ctx, authReq)
 	if err != nil {
 		return "", 0, err
 	}
 	validity = exp.Sub(time.Now().UTC())
-	if client.AccessTokenType() == AccessTokenTypeJWT {
+	if accessTokenType == AccessTokenTypeJWT {
 		token, err = CreateJWT(creator.Issuer(), authReq, exp, id, creator.Signer())
 		return
 	}
@@ -75,7 +82,7 @@ func CreateBearerToken(id string, crypto Crypto) (string, error) {
 	return crypto.Encrypt(id)
 }
 
-func CreateJWT(issuer string, authReq AuthRequest, exp time.Time, id string, signer Signer) (string, error) {
+func CreateJWT(issuer string, authReq TokenRequest, exp time.Time, id string, signer Signer) (string, error) {
 	now := time.Now().UTC()
 	nbf := now
 	claims := &oidc.AccessTokenClaims{
diff --git a/pkg/op/tokenrequest.go b/pkg/op/tokenrequest.go
index 7de2a70..f208fcc 100644
--- a/pkg/op/tokenrequest.go
+++ b/pkg/op/tokenrequest.go
@@ -3,7 +3,6 @@ package op
 import (
 	"context"
 	"errors"
-	"fmt"
 	"net/http"
 
 	"github.com/caos/oidc/pkg/oidc"
@@ -22,7 +21,7 @@ type Exchanger interface {
 
 type VerifyExchanger interface {
 	Exchanger
-	Verifier() rp.Verifier
+	ClientJWTVerifier() rp.Verifier
 }
 
 func CodeExchange(w http.ResponseWriter, r *http.Request, exchanger Exchanger) {
@@ -121,17 +120,31 @@ func AuthorizeCodeChallenge(ctx context.Context, tokenReq *oidc.AccessTokenReque
 	return authReq, nil
 }
 
+type ClientJWTVerifier struct {
+	claims *oidc.JWTTokenRequest
+	Storage
+}
+
+func (c *ClientJWTVerifier) Issuer() string {
+	client, err := Storage.GetClientByClientID(context.TODO(), c.claims.Issuer)
+	return client.GetID()
+}
+
 func JWTExchange(w http.ResponseWriter, r *http.Request, exchanger VerifyExchanger) {
 	assertion, err := ParseJWTTokenRequest(r, exchanger.Decoder())
 	if err != nil {
 		RequestError(w, r, err)
 	}
-	claims, err := exchanger.Verifier().Verify(r.Context(), "", assertion)
+	claims := new(oidc.JWTTokenRequest)
+	//var keyset oidc.KeySet
+	verifier := new(ClientJWTVerifier)
+	verifier.claims = claims
+	err = verifier.VerifyToken(r.Context(), assertion, claims)
+	if err != nil {
+		RequestError(w, r, err)
+	}
 
-	fmt.Println(claims, err)
-	var authReq AuthRequest
-	var client Client
-	resp, err := CreateJWTTokenResponse(r.Context(), authReq, client, exchanger)
+	resp, err := CreateJWTTokenResponse(r.Context(), claims, exchanger)
 	if err != nil {
 		RequestError(w, r, err)
 		return
@@ -139,7 +152,7 @@ func JWTExchange(w http.ResponseWriter, r *http.Request, exchanger VerifyExchang
 	utils.MarshalJSON(w, resp)
 }
 
-func ParseJWTTokenRequest(r *http.Request, decoder *schema.Decoder) (string, error) {
+func ParseJWTTokenRequest(r *http.Request, decoder utils.Decoder) (string, error) {
 	err := r.ParseForm()
 	if err != nil {
 		return "", ErrInvalidRequest("error parsing form")
diff --git a/pkg/rp/default_verifier.go b/pkg/rp/default_verifier.go
index a75eddc..2820e39 100644
--- a/pkg/rp/default_verifier.go
+++ b/pkg/rp/default_verifier.go
@@ -1,16 +1,10 @@
 package rp
 
 import (
-	"bytes"
 	"context"
-	"encoding/base64"
-	"encoding/json"
 	"fmt"
-	"strings"
 	"time"
 
-	"gopkg.in/square/go-jose.v2"
-
 	"github.com/caos/oidc/pkg/oidc"
 	"github.com/caos/oidc/pkg/utils"
 )
@@ -24,9 +18,6 @@ type DefaultVerifier struct {
 //ConfFunc is the type for providing dynamic options to the DefaultVerfifier
 type ConfFunc func(*verifierConfig)
 
-//ACRVerifier specifies the function to be used by the `DefaultVerifier` for validating the acr claim
-type ACRVerifier func(string) error
-
 //NewDefaultVerifier creates `DefaultVerifier` with the given
 //issuer, clientID, keyset and possible configOptions
 func NewDefaultVerifier(issuer, clientID string, keySet oidc.KeySet, confOpts ...ConfFunc) Verifier {
@@ -90,7 +81,7 @@ func WithNonce(nonce string) func(*verifierConfig) {
 }
 
 //WithACRVerifier sets the verifier for the acr claim
-func WithACRVerifier(verifier ACRVerifier) func(*verifierConfig) {
+func WithACRVerifier(verifier oidc.ACRVerifier) func(*verifierConfig) {
 	return func(conf *verifierConfig) {
 		conf.acr = verifier
 	}
@@ -117,7 +108,7 @@ type verifierConfig struct {
 	ignoreAudience    bool
 	ignoreExpiration  bool
 	iat               *iatConfig
-	acr               ACRVerifier
+	acr               oidc.ACRVerifier
 	maxAge            time.Duration
 	supportedSignAlgs []string
 
@@ -134,10 +125,10 @@ type iatConfig struct {
 
 //DefaultACRVerifier implements `ACRVerifier` returning an error
 //if non of the provided values matches the acr claim
-func DefaultACRVerifier(possibleValues []string) ACRVerifier {
+func DefaultACRVerifier(possibleValues []string) oidc.ACRVerifier {
 	return func(acr string) error {
 		if !utils.Contains(possibleValues, acr) {
-			return ErrAcrInvalid(possibleValues, acr)
+			return fmt.Errorf("expected one of: %v, got: %q", possibleValues, acr)
 		}
 		return nil
 	}
@@ -148,88 +139,13 @@ func DefaultACRVerifier(possibleValues []string) ACRVerifier {
 //and https://openid.net/specs/openid-connect-core-1_0.html#CodeFlowTokenValidation
 func (v *DefaultVerifier) Verify(ctx context.Context, accessToken, idTokenString string) (*oidc.IDTokenClaims, error) {
 	v.config.now = time.Now().UTC()
-	// idToken, err := v.VerifyIDToken(ctx, idTokenString)
-	// if err != nil {
-	// 	return nil, err
-	// }
-	// if err := v.verifyAccessToken(accessToken, idToken.AccessTokenHash, idToken.Signature); err != nil { //TODO: sig from token
-	// 	return nil, err
-	// }
-	// return idToken, nil
-
-	// TODO: verifiy
-	decrypted, err := v.decryptToken(idTokenString)
-	if err != nil {
-		return nil, err
-	}
-	claims, _, err := v.parseToken(decrypted)
-	if err != nil {
-		return nil, err
-	}
-	return claims, nil
+	return VerifyTokens(ctx, accessToken, idTokenString, v)
 }
 
 //Verify implements the `VerifyIDToken` method of the `Verifier` interface
 //according to https://openid.net/specs/openid-connect-core-1_0.html#IDTokenValidation
 func (v *DefaultVerifier) VerifyIDToken(ctx context.Context, idTokenString string) (*oidc.IDTokenClaims, error) {
-	//1. if encrypted --> decrypt
-	decrypted, err := v.decryptToken(idTokenString)
-	if err != nil {
-		return nil, err
-	}
-	claims, payload, err := v.parseToken(decrypted)
-	if err != nil {
-		return nil, err
-	}
-	// token, err := jwt.ParseWithClaims(decrypted, claims, func(token *jwt.Token) (interface{}, error) {
-	//2, check issuer (exact match)
-	if err := v.checkIssuer(claims.Issuer); err != nil {
-		return nil, err
-	}
-
-	//3. check aud (aud must contain client_id, all aud strings must be allowed)
-	if err = v.checkAudience(claims.Audiences); err != nil {
-		return nil, err
-	}
-
-	if err = v.checkAuthorizedParty(claims.Audiences, claims.AuthorizedParty); err != nil {
-		return nil, err
-	}
-
-	//6. check signature by keys
-	//7. check alg default is rs256
-	//8. check if alg is mac based (hs...) -> audience contains client_id. for validation use utf-8 representation of your client_secret
-	claims.Signature, err = v.checkSignature(ctx, decrypted, payload)
-	if err != nil {
-		return nil, err
-	}
-
-	//9. check exp before now
-	if err = v.checkExpiration(claims.Expiration); err != nil {
-		return nil, err
-	}
-
-	//10. check iat duration is optional (can be checked)
-	if err = v.checkIssuedAt(claims.IssuedAt); err != nil {
-		return nil, err
-	}
-
-	//11. check nonce (check if optional possible) id_token.nonce == sentNonce
-	if err = v.checkNonce(claims.Nonce); err != nil {
-		return nil, err
-	}
-
-	//12. if acr requested check acr
-	if err = v.checkAuthorizationContextClassReference(claims.AuthenticationContextClassReference); err != nil {
-		return nil, err
-	}
-
-	//13. if auth_time requested check if auth_time is less than max age
-	if err = v.checkAuthTime(claims.AuthTime); err != nil {
-		return nil, err
-	}
-
-	return claims, nil
+	return VerifyIDToken(ctx, idTokenString, v)
 }
 
 func (v *DefaultVerifier) now() time.Time {
@@ -239,161 +155,34 @@ func (v *DefaultVerifier) now() time.Time {
 	return v.config.now
 }
 
-func (v *DefaultVerifier) parseToken(tokenString string) (*oidc.IDTokenClaims, []byte, error) {
-	parts := strings.Split(tokenString, ".")
-	if len(parts) != 3 {
-		return nil, nil, ValidationError("token contains an invalid number of segments") //TODO: err NewValidationError("token contains an invalid number of segments", ValidationErrorMalformed)
-	}
-	payload, err := base64.RawURLEncoding.DecodeString(parts[1])
-	if err != nil {
-		return nil, nil, fmt.Errorf("oidc: malformed jwt payload: %v", err)
-	}
-	idToken := new(oidc.IDTokenClaims)
-	err = json.Unmarshal(payload, idToken)
-	return idToken, payload, err
+func (v *DefaultVerifier) Issuer() string {
+	return v.config.issuer
 }
 
-func (v *DefaultVerifier) checkIssuer(issuer string) error {
-	if v.config.issuer != issuer {
-		return ErrIssuerInvalid(v.config.issuer, issuer)
-	}
-	return nil
+func (v *DefaultVerifier) ClientID() string {
+	return v.config.clientID
 }
 
-func (v *DefaultVerifier) checkAudience(audiences []string) error {
-	if v.config.ignoreAudience {
-		return nil
-	}
-	if !utils.Contains(audiences, v.config.clientID) {
-		return ErrAudienceMissingClientID(v.config.clientID)
-	}
-
-	//TODO: check aud trusted
-	return nil
+func (v *DefaultVerifier) SupportedSignAlgs() []string {
+	return v.config.supportedSignAlgs
 }
 
-//4. if multiple aud strings --> check if azp
-//5. if azp --> check azp == client_id
-func (v *DefaultVerifier) checkAuthorizedParty(audiences []string, authorizedParty string) error {
-	if v.config.ignoreAudience {
-		return nil
-	}
-	if len(audiences) > 1 {
-		if authorizedParty == "" {
-			return ErrAzpMissing()
-		}
-	}
-	if authorizedParty != "" && authorizedParty != v.config.clientID {
-		return ErrAzpInvalid(authorizedParty, v.config.clientID)
-	}
-	return nil
+func (v *DefaultVerifier) KeySet() oidc.KeySet {
+	return v.keySet
 }
 
-func (v *DefaultVerifier) checkSignature(ctx context.Context, idTokenString string, payload []byte) (jose.SignatureAlgorithm, error) {
-	jws, err := jose.ParseSigned(idTokenString)
-	if err != nil {
-		return "", err
-	}
-	if len(jws.Signatures) == 0 {
-		return "", ErrSignatureMissing()
-	}
-	if len(jws.Signatures) > 1 {
-		return "", ErrSignatureMultiple()
-	}
-	sig := jws.Signatures[0]
-	supportedSigAlgs := v.config.supportedSignAlgs
-	if len(supportedSigAlgs) == 0 {
-		supportedSigAlgs = []string{"RS256"}
-	}
-	if !utils.Contains(supportedSigAlgs, sig.Header.Algorithm) {
-		return "", fmt.Errorf("oidc: id token signed with unsupported algorithm, expected %q got %q", supportedSigAlgs, sig.Header.Algorithm)
-	}
-
-	signedPayload, err := v.keySet.VerifySignature(ctx, jws)
-	if err != nil {
-		return "", err
-	}
-
-	if !bytes.Equal(signedPayload, payload) {
-		return "", ErrSignatureInvalidPayload()
-	}
-	return jose.SignatureAlgorithm(sig.Header.Algorithm), nil
+func (v *DefaultVerifier) ACR() oidc.ACRVerifier {
+	return v.config.acr
 }
 
-func (v *DefaultVerifier) checkExpiration(expiration time.Time) error {
-	if v.config.ignoreExpiration {
-		return nil
-	}
-	expiration = expiration.Round(time.Second)
-	if !v.now().Before(expiration) {
-		return ErrExpInvalid(expiration)
-	}
-	return nil
+func (v *DefaultVerifier) MaxAge() time.Duration {
+	return v.config.maxAge
 }
 
-func (v *DefaultVerifier) checkIssuedAt(issuedAt time.Time) error {
-	if v.config.iat.ignore {
-		return nil
-	}
-	issuedAt = issuedAt.Round(time.Second)
-	offset := v.now().Add(v.config.iat.offset).Round(time.Second)
-	if issuedAt.After(offset) {
-		return ErrIatInFuture(issuedAt, offset)
-	}
-	if v.config.iat.maxAge == 0 {
-		return nil
-	}
-	maxAge := v.now().Add(-v.config.iat.maxAge).Round(time.Second)
-	if issuedAt.Before(maxAge) {
-		return ErrIatToOld(maxAge, issuedAt)
-	}
-	return nil
-}
-func (v *DefaultVerifier) checkNonce(nonce string) error {
-	if v.config.nonce == "" {
-		return nil
-	}
-	if v.config.nonce != nonce {
-		return ErrNonceInvalid(v.config.nonce, nonce)
-	}
-	return nil
-}
-func (v *DefaultVerifier) checkAuthorizationContextClassReference(acr string) error {
-	if v.config.acr != nil {
-		return v.config.acr(acr)
-	}
-	return nil
-}
-func (v *DefaultVerifier) checkAuthTime(authTime time.Time) error {
-	if v.config.maxAge == 0 {
-		return nil
-	}
-	if authTime.IsZero() {
-		return ErrAuthTimeNotPresent()
-	}
-	authTime = authTime.Round(time.Second)
-	maxAge := v.now().Add(-v.config.maxAge).Round(time.Second)
-	if authTime.Before(maxAge) {
-		return ErrAuthTimeToOld(maxAge, authTime)
-	}
-	return nil
+func (v *DefaultVerifier) MaxAgeIAT() time.Duration {
+	return v.config.iat.maxAge
 }
 
-func (v *DefaultVerifier) decryptToken(tokenString string) (string, error) {
-	return tokenString, nil //TODO: impl
-}
-
-func (v *DefaultVerifier) verifyAccessToken(accessToken, atHash string, sigAlgorithm jose.SignatureAlgorithm) error {
-	if atHash == "" {
-		return nil
-	}
-
-	actual, err := oidc.ClaimHash(accessToken, sigAlgorithm)
-	if err != nil {
-		return err
-	}
-	if actual != atHash {
-		return ErrAtHash()
-	}
-	return nil
+func (v *DefaultVerifier) Offset() time.Duration {
+	return v.config.iat.offset
 }
diff --git a/pkg/rp/error.go b/pkg/rp/error.go
deleted file mode 100644
index fa0ece9..0000000
--- a/pkg/rp/error.go
+++ /dev/null
@@ -1,67 +0,0 @@
-package rp
-
-import (
-	"fmt"
-	"time"
-)
-
-var (
-	ErrIssuerInvalid = func(expected, actual string) *validationError {
-		return ValidationError("Issuer does not match. Expected: %s, got: %s", expected, actual)
-	}
-	ErrAudienceMissingClientID = func(clientID string) *validationError {
-		return ValidationError("Audience is not valid. Audience must contain client_id (%s)", clientID)
-	}
-	ErrAzpMissing = func() *validationError {
-		return ValidationError("Authorized Party is not set. If Token is valid for multiple audiences, azp must not be empty")
-	}
-	ErrAzpInvalid = func(azp, clientID string) *validationError {
-		return ValidationError("Authorized Party is not valid. azp (%s) must be equal to client_id (%s)", azp, clientID)
-	}
-	ErrExpInvalid = func(exp time.Time) *validationError {
-		return ValidationError("Token has expired %v", exp)
-	}
-	ErrIatInFuture = func(exp, now time.Time) *validationError {
-		return ValidationError("IssuedAt of token is in the future (%v, now with offset: %v)", exp, now)
-	}
-	ErrIatToOld = func(maxAge, iat time.Time) *validationError {
-		return ValidationError("IssuedAt of token must not be older than %v, but was %v (%v to old)", maxAge, iat, maxAge.Sub(iat))
-	}
-	ErrNonceInvalid = func(expected, actual string) *validationError {
-		return ValidationError("nonce does not match. Expected: %s, got: %s", expected, actual)
-	}
-	ErrAcrInvalid = func(expected []string, actual string) *validationError {
-		return ValidationError("acr is invalid. Expected one of: %v, got: %s", expected, actual)
-	}
-
-	ErrAuthTimeNotPresent = func() *validationError {
-		return ValidationError("claim `auth_time` of token is missing")
-	}
-	ErrAuthTimeToOld = func(maxAge, authTime time.Time) *validationError {
-		return ValidationError("Auth Time of token must not be older than %v, but was %v (%v to old)", maxAge, authTime, maxAge.Sub(authTime))
-	}
-	ErrSignatureMissing = func() *validationError {
-		return ValidationError("id_token does not contain a signature")
-	}
-	ErrSignatureMultiple = func() *validationError {
-		return ValidationError("id_token contains multiple signatures")
-	}
-	ErrSignatureInvalidPayload = func() *validationError {
-		return ValidationError("Signature does not match Payload")
-	}
-	ErrAtHash = func() *validationError {
-		return ValidationError("at_hash does not correspond to access token")
-	}
-)
-
-func ValidationError(message string, args ...interface{}) *validationError {
-	return &validationError{fmt.Sprintf(message, args...)} //TODO: impl
-}
-
-type validationError struct {
-	message string
-}
-
-func (v *validationError) Error() string {
-	return v.message
-}
diff --git a/pkg/rp/verifier.go b/pkg/rp/verifier.go
index 5add60f..61caed1 100644
--- a/pkg/rp/verifier.go
+++ b/pkg/rp/verifier.go
@@ -3,11 +3,12 @@ package rp
 import (
 	"context"
 
+	"gopkg.in/square/go-jose.v2"
+
 	"github.com/caos/oidc/pkg/oidc"
 )
 
-//Verifier implement the Token Response Validation as defined in OIDC specification
-//https://openid.net/specs/openid-connect-core-1_0.html#TokenResponseValidation
+//deprecated: Use IDTokenVerifier or oidc.Verifier
 type Verifier interface {
 
 	//Verify checks the access_token and id_token and returns the `id token claims`
@@ -16,3 +17,100 @@ type Verifier interface {
 	//VerifyIDToken checks the id_token only and returns its `id token claims`
 	VerifyIDToken(ctx context.Context, idTokenString string) (*oidc.IDTokenClaims, error)
 }
+
+type IDTokenVerifier interface {
+	oidc.Verifier
+}
+
+//VerifyTokens implement the Token Response Validation as defined in OIDC specification
+//https://openid.net/specs/openid-connect-core-1_0.html#TokenResponseValidation
+func VerifyTokens(ctx context.Context, accessToken, idTokenString string, v IDTokenVerifier) (*oidc.IDTokenClaims, error) {
+	idToken, err := VerifyIDToken(ctx, idTokenString, v)
+	if err != nil {
+		return nil, err
+	}
+	if err := VerifyAccessToken(accessToken, idToken.AccessTokenHash, idToken.Signature); err != nil {
+		return nil, err
+	}
+	return idToken, nil
+}
+
+//VerifyIDToken validates the id token according to
+//https://openid.net/specs/openid-connect-core-1_0.html#IDTokenValidation
+func VerifyIDToken(ctx context.Context, token string, v IDTokenVerifier) (*oidc.IDTokenClaims, error) {
+	claims := new(oidc.IDTokenClaims)
+
+	decrypted, err := oidc.DecryptToken(token)
+	if err != nil {
+		return nil, err
+	}
+	payload, err := oidc.ParseToken(decrypted, claims)
+	if err != nil {
+		return nil, err
+	}
+	//2, check issuer (exact match)
+	if err := oidc.CheckIssuer(claims.GetIssuer(), v); err != nil {
+		return nil, err
+	}
+
+	//3. check aud (aud must contain client_id, all aud strings must be allowed)
+	if err = oidc.CheckAudience(claims.GetAudience(), v); err != nil {
+		return nil, err
+	}
+
+	if err = oidc.CheckAuthorizedParty(claims.GetAudience(), claims.GetAuthorizedParty(), v); err != nil {
+		return nil, err
+	}
+
+	//6. check signature by keys
+	//7. check alg default is rs256
+	//8. check if alg is mac based (hs...) -> audience contains client_id. for validation use utf-8 representation of your client_secret
+	if err = oidc.CheckSignature(ctx, decrypted, payload, claims, v); err != nil {
+		return nil, err
+	}
+
+	//9. check exp before now
+	if err = oidc.CheckExpiration(claims.GetExpiration(), v); err != nil {
+		return nil, err
+	}
+
+	//10. check iat duration is optional (can be checked)
+	if err = oidc.CheckIssuedAt(claims.GetIssuedAt(), v); err != nil {
+		return nil, err
+	}
+
+	/*
+		//11. check nonce (check if optional possible) id_token.nonce == sentNonce
+		if err = oidc.CheckNonce(claims.GetNonce()); err != nil {
+			return nil, err
+		}
+	*/
+
+	//12. if acr requested check acr
+	if err = oidc.CheckAuthorizationContextClassReference(claims.GetAuthenticationContextClassReference(), v); err != nil {
+		return nil, err
+	}
+
+	//13. if auth_time requested check if auth_time is less than max age
+	if err = oidc.CheckAuthTime(claims.GetAuthTime(), v); err != nil {
+		return nil, err
+	}
+	return claims, nil
+}
+
+//VerifyAccessToken validates the access token according to
+//https://openid.net/specs/openid-connect-core-1_0.html#CodeFlowTokenValidation
+func VerifyAccessToken(accessToken, atHash string, sigAlgorithm jose.SignatureAlgorithm) error {
+	if atHash == "" {
+		return nil
+	}
+
+	actual, err := oidc.ClaimHash(accessToken, sigAlgorithm)
+	if err != nil {
+		return err
+	}
+	if actual != atHash {
+		return oidc.ErrAtHash
+	}
+	return nil
+}
diff --git a/pkg/rp/verity.go b/pkg/rp/verity.go
new file mode 100644
index 0000000..189ce90
--- /dev/null
+++ b/pkg/rp/verity.go
@@ -0,0 +1,9 @@
+package rp
+
+import (
+	"context"
+
+	"gopkg.in/square/go-jose.v2"
+
+	"github.com/caos/oidc/pkg/oidc"
+)