All Java installations support only up to 128-bit AES by default. Oracle calls that "strong encryption". You can upgrade to "unlimited strength" by changing som

All Java installations support only up to 128-bit AES by default. Oracle calls that "strong encryption". You can upgrade to "unlimited strength" by changing some policy files, after which 256-bit AES will be possible. I don't know if that's what you're seeing, but there's definitely a class of clients that do not support 256-bit AES.