diff --git a/auth-server/server.go b/auth-server/server.go
index 3959026..2135e91 100644
--- a/auth-server/server.go
+++ b/auth-server/server.go
@@ -22,9 +22,9 @@ import (
 
 type IBlockchainStorage interface {
 	GetByID(ctx context.Context, id string) (oauth2.ClientInfo, error) // read
-	Set(id string, cli oauth2.ClientInfo) (err error)                  // create and update
-	Delete(id string) (err error)                                      // delete
-	CheckPassword(id string, secret util.Uint256) (bool, error)        // CheckUser
+	Set(clt oauth2.ClientInfo) error                                   // create and update
+	Delete(id string) error                                            // delete
+	CheckPassword(id string, secret string) (bool, error)              // CheckUser
 }
 
 type BlockchainStorage struct {
@@ -32,8 +32,8 @@ type BlockchainStorage struct {
 }
 
 type StorageClientInfo struct {
-	login    string
-	password util.Uint256
+	id     string
+	secret string
 }
 
 func NewBlockchainStorage(actor Actor, hash util.Uint160) *BlockchainStorage {
@@ -46,21 +46,40 @@ func (storage BlockchainStorage) GetByID(ctx context.Context, id string) (oauth2
 		return nil, err
 	}
 
-	return &StorageClientInfo{login: id, password: password}, nil
+	return &StorageClientInfo{id: id, secret: password.StringLE()}, nil
 }
 
-func (storage BlockchainStorage) Set(id string, cli oauth2.ClientInfo) (err error) {
-	// how to check whether user exists? (util.Uint256 conversion)
+func (storage BlockchainStorage) Set(clt oauth2.ClientInfo) error {
+	password, decodeErr := util.Uint256DecodeStringLE(clt.GetSecret())
+	if decodeErr != nil {
+		return decodeErr
+	}
+
+	_, _, err := storage.contract.UpdateUser(clt.GetID(), password)
+	if err != nil {
+		_, _, err = storage.contract.CreateUser(clt.GetID(), password)
+
+		if err != nil {
+			return errors.New("Something went wrong")
+		}
+	}
+
+	return nil
 }
 
-func (storage BlockchainStorage) Delete(id string) (err error) {
-	// how to use hash and ValidUntilBlock?
-	_, _, err = storage.contract.DeleteUser(id)
-	return err
+func (storage BlockchainStorage) Delete(id string) error {
+	// should we use hash and ValidUntilBlock?
+	_, _, res := storage.contract.DeleteUser(id)
+	return res
 }
 
-func (storage BlockchainStorage) CheckPassword(id string, secret util.Uint256) (bool, error) {
-	_, err := storage.contract.CheckUser(id, secret)
+func (storage BlockchainStorage) CheckPassword(id string, secret string) (bool, error) {
+	password, decodeErr := util.Uint256DecodeStringLE(secret)
+	if decodeErr != nil {
+		return false, decodeErr
+	}
+
+	_, err := storage.contract.CheckUser(id, password)
 	if err != nil {
 		return false, err
 	}
@@ -69,11 +88,11 @@ func (storage BlockchainStorage) CheckPassword(id string, secret util.Uint256) (
 }
 
 func (model StorageClientInfo) GetID() string {
-	return model.login
+	return model.id
 }
 
 func (model StorageClientInfo) GetSecret() string {
-	return model.password.String()
+	return model.secret
 }
 
 func (model StorageClientInfo) GetDomain() string {