How to expand DH key size to 2048 in java 8

Question

I read a lot of posts saying that in java 8 it is possible to expand the DH key size to 2048. They say it is possible from the system property by changing the value of: jdk.tls.ephemeralDHKeySize to 2048. I tried to figure out where and how to do this and could not find. Where can I find this variable or property? which file? path? I am using windows.

Answer 1

This is a system property, so you could set it via -Djdk.tls.ephemeralDHKeySize=2048 as a JVM argument or via System.setProperty within the code. (I haven't checked for this property, but some properties are read only once by the library that uses them, and then cached permanently during the execution time of the JVM, so you'd generally want to set that setting early enough if you set it within the code.)

The acceptable values are documented in the JSSE reference guide: "Customizing Size of Ephemeral Diffie-Hellman Keys".