This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Originally posted by Raghven k b: Hi, Thanks for opening.
I have a basic question, like when do we need to sign a jar ? what is the purpose ?
Signing a jar is basically used to verify a trusted source. When you sign a jar with your digital signature (based on your private key), you place a mark into the jar file that could not have been done by anyone but you.
The signature is also a checksum of the Jar file, so if the jar get corrupted or modified in transit, the signature is invalid.
On the other side, your public key is placed into the keystore of the system that trust you. This will be used to verify your signature.
Currently, I believe this is mainly used for applets. Using signed jar files, and setting security properties on client browsers, applets can have access to disk, network, and other stuff that they don't normally have access to.