Recently discovered the need to upgrade our DH key exchange length (used for TLS) from 1024 bits to 2048 bits (due to Logjam exploit and other factors). The question is: How will making that change affect client compatibility? Is there an official list of OS's/browsers that can support 2048-bit crypto for key exchange when using TLS? I've only seen mutterings about older client versions of Java (
Modern browsers will be perfectly happy accepting 2048-bit DH moduli. You can verify that your site's TLS configuration is compatible with popular browsers by using SSLTest. Only (very) outdated versions of Java tend to have problems with DH moduli larger than 1024 bits.