Decrypt credentials defined in Jenkins and list values.

def creds = com.cloudbees.plugins.credentials.CredentialsProvider.lookupCredentials(
    com.cloudbees.plugins.credentials.common.StandardUsernameCredentials.class,
    Jenkins.instance,
    null,
    null
);
for (c in creds) {
  if (c.properties.privateKeySource) {
	  println("ID: " + c.id)
    println("UserName: " + c.username)
    println("Description: " + c.description)
	  println("Private Key: " + c.getPrivateKey() )
  }
}

Decrypt the password if you got its HASH.

println(hudson.util.Secret.decrypt("{HASHxxxxx=}"))
# or /////
println(hudson.util.Secret.fromString("{HASHxxxxx=}").getPlainText())

Trigger build by url

# Run when the anonymous user has the build permission
curl <http://127.0.0.1:8080/job/Trigger_Remote_Demo/build?token=My-token>
# Send request with credentials
curl -u username:api_token <http://127.0.0.1:8080/job/Trigger_Remote_Demo/build>
# Build with Parameter
curl -u username:api_token <http://127.0.0.1:8080/job/Trigger_Remote_Demo/buildWithParameters?para1=val1&para2=val2>