Decrypting Jenkins Password

jenkins-decrypt.groovy

#To Decrypt Jenkins Password from credentials.xml
#<username>jenkins</username>
#<passphrase>your-sercret-hash-S0SKVKUuFfUfrY3UhhUC3J</passphrase>


#go to the jenkins url 
http://jenkins-host/script

#In the console paste the script
hashed_pw='your-sercret-hash-S0SKVKUuFfUfrY3UhhUC3J'
passwd = hudson.util.Secret.decrypt(hashed_pw)
println(passwd)

---
String key = "Vo1hb2DfqHO5U0AdneAmVon1B54VLZr6+2I1AoeONhw="
def secret = hudson.util.Secret.fromString(key)
println(secret.getPlainText())

This key is just an example, if your try, you would be get a null value, since this key was encrypted with a secret hash. Each installation of Jenkins has a different secret file.
There are hash exist with and without curly braces, if your key contains curly braces you must include this in key variable.