Signature filename is now hash of attributes

attributes.go

@@ -8,6 +8,8 @@ import (
 	"math/big"
 	"time"
 
+	"encoding/hex"
+
 	"github.com/mhe/gabi"
 )
 
@@ -66,6 +68,15 @@ func (al *AttributeList) Info() *CredentialInfo {
 	return al.info
 }
 
+func (al *AttributeList) hash() string {
+	bytes := []byte{}
+	for _, i := range al.Ints {
+		bytes = append(bytes, i.Bytes()...)
+	}
+	shasum := sha256.Sum256(bytes)
+	return hex.EncodeToString(shasum[:])
+}
+
 // Strings converts the current instance to human-readable strings.
 func (al *AttributeList) Strings() []string {
 	if al.strings == nil {

credential.go

@@ -13,6 +13,7 @@ import (
 type credential struct {
 	*gabi.Credential
 	*MetadataAttribute
+	attrs *AttributeList
 }
 
 // CredentialInfo contains all information of an IRMA credential.
@@ -67,6 +68,13 @@ func newCredential(gabicred *gabi.Credential, store *ConfigurationStore) (*crede
 	return cred, nil
 }
 
+func (cred *credential) AttributeList() *AttributeList {
+	if cred.attrs == nil {
+		cred.attrs = NewAttributeListFromInts(cred.Credential.Attributes[1:], cred.MetadataAttribute.store)
+	}
+	return cred.attrs
+}
+
 // Len implements sort.Interface.
 func (cl CredentialInfoList) Len() int {
 	return len(cl)

manager.go

@@ -88,8 +88,7 @@ func (cm *CredentialManager) credential(id CredentialTypeIdentifier, counter int
 		if attrs == nil { // We do not have the requested cred
 			return
 		}
-		ints := append([]*big.Int{cm.secretkey}, attrs.Ints...)
-		sig, err := cm.loadSignature(id, counter)
+		sig, err := cm.loadSignature(attrs)
 		if err != nil {
 			return nil, err
 		}
@@ -97,8 +96,7 @@ func (cm *CredentialManager) credential(id CredentialTypeIdentifier, counter int
 			err = errors.New("signature file not found")
 			return nil, err
 		}
-		meta := MetadataFromInt(ints[1], cm.Store)
-		pk, err := meta.PublicKey()
+		pk, err := attrs.PublicKey()
 		if err != nil {
 			return nil, err
 		}
@@ -106,7 +104,7 @@ func (cm *CredentialManager) credential(id CredentialTypeIdentifier, counter int
 			return nil, errors.New("unknown public key")
 		}
 		cred, err := newCredential(&gabi.Credential{
-			Attributes: ints,
+			Attributes: append([]*big.Int{cm.secretkey}, attrs.Ints...),
 			Signature:  sig,
 			Pk:         pk,
 		}, cm.Store)
@@ -122,9 +120,8 @@ func (cm *CredentialManager) credential(id CredentialTypeIdentifier, counter int
 // addCredential adds the specified credential to the CredentialManager, saving its signature
 // imediately, and optionally cm.attributes as well.
 func (cm *CredentialManager) addCredential(cred *credential, storeAttributes bool) (err error) {
-	attrs := NewAttributeListFromInts(cred.Attributes[1:], cm.Store)
 	id := cred.CredentialType().Identifier()
-	cm.attributes[id] = append(cm.attrs(id), attrs)
+	cm.attributes[id] = append(cm.attrs(id), cred.AttributeList())
 
 	if _, exists := cm.credentials[id]; !exists {
 		cm.credentials[id] = make(map[int]*credential)
@@ -161,7 +158,7 @@ func (cm *CredentialManager) Candidates(disjunction *AttributeDisjunction) []*At
 			if attribute.IsCredential() {
 				candidates = append(candidates, id)
 			} else {
-				attrs := NewAttributeListFromInts(cred.Attributes[1:], cm.Store)
+				attrs := cred.AttributeList()
 				val := attrs.Attribute(attribute)
 				if val == "" { // This won't handle empty attributes correctly
 					continue

storage.go

@@ -6,7 +6,6 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
-	"strconv"
 
 	"crypto/rand"
 	"encoding/hex"
@@ -185,8 +184,8 @@ func (cm *CredentialManager) path(file string) string {
 	return cm.storagePath + "/" + file
 }
 
-func (cm *CredentialManager) signatureFilename(id string, counter int) string {
-	return cm.path(signaturesDir) + "/" + id + "-" + strconv.Itoa(counter)
+func (cm *CredentialManager) signatureFilename(attrs *AttributeList) string {
+	return cm.path(signaturesDir) + "/" + attrs.hash()
 }
 
 // ensureStorageExists initializes the credential storage folder,
@@ -257,7 +256,7 @@ func (cm *CredentialManager) storeSignature(cred *credential, counter int) (err
 	}
 
 	// TODO existence check
-	filename := cm.signatureFilename(cred.CredentialType().Identifier().String(), counter)
+	filename := cm.signatureFilename(cred.AttributeList())
 	err = ioutil.WriteFile(filename, credbytes, 0600)
 	return
 }
@@ -291,8 +290,8 @@ func (cm *CredentialManager) storePaillierKeys() (err error) {
 	return
 }
 
-func (cm *CredentialManager) loadSignature(id CredentialTypeIdentifier, counter int) (signature *gabi.CLSignature, err error) {
-	sigpath := cm.signatureFilename(id.String(), counter)
+func (cm *CredentialManager) loadSignature(attrs *AttributeList) (signature *gabi.CLSignature, err error) {
+	sigpath := cm.signatureFilename(attrs)
 	exists, err := PathExists(sigpath)
 	if err != nil {
 		return