Import the Certificate as a Trusted Certificate
Suppose that you are Ruth and have received from Stan Smith
The signed JAR file
sContract.jarcontaining a contract
StanSmith.cercontaining the public key certificate for the public key corresponding to the private key used to sign the JAR file
Before you can use the
jarsigner tool to check the authenticity of the JAR file's signature, you need to import Stan's certificate into your keystore.
Even though you (acting as Stan) created these files and they haven't actually been transported anywhere, you can simulate being someone other than the creater and sender, Stan. Acting as Ruth, type the following command to create a keystore named
exampleruthstore and import the certificate into an entry with an alias of
keytool -import -alias stan -file StanSmith.cer -keystore exampleruthstore
Since the keystore doesn't yet exist,
keytool will create it for you. It will prompt you for a keystore password.
keytool prints the certificate information and asks you to verify it; For example, by comparing the displayed certificate fingerprints with those obtained from another (trusted) source of information. (Each fingerprint is a relatively short number that uniquely and reliably identifies the certificate.) For example, in the real world you can phone Stan and ask him what the fingerprints should be. He can get the fingerprints of the
StanSmith.cer file he created by executing the command
keytool -printcert -file StanSmith.cer
If the fingerprints he sees are the same as the ones reported to you by
keytool , then you both can assume that the certificate has not been modified in transit. You can safely let
keytool procede to place a "trusted certificate" entry into your keystore. This entry contains the public key certificate data from the file
keytool assigns the alias
stan to this new entry.