Zitat von Martijn Brinkers <martijn(a)djigzo.com>om>: It might also depend on the target. For e-Mail it should be ok as long as most of the users has powerful devices (PC alike). With handhelds as primary target it could already matter if the keysize is "too big" as the time needed is non linear (http://www.javamex.com/tutorials/cryptography/rsa_key_length.shtml). On the other hand e-mail is not a that sensitiv for some delay in processing like for example https, so for advanced or long term security it is reasonable to go for 4096/2048bits. A quick glance on the root CAs issued after ~2005 in our Gateway keystore lead to around one-third with 4096 and two-third with 2048 and some minority still at 1024 bits RSA. So if the somewhat bigger CAs use 4096 bits it should be no problem from interoperable point of view. So +1 for Martijn's suggestion Regards Andreas