Patch servers, patch clients and corresponding methods are provided that may increase secret protection and key loss tolerance. A patch server includes a first key generation platform and a second key generation platform different from the first one. A first and second private key group containing a plurality of first or second private keys, respectively, is generated using the first or second key generation platform, respectively. One of the first private keys is selected from the first private key group, and one of the second private keys is selected from the second private key group. A first digital signature is generated based on the patch and the first selected private key. A second digital signature is generated based on the patch and the second selected private key. The patch is transmitted to the patch client together with the first and second digital signatures.