Decryption algorithm from original password and encrypted password ?

I have passwords encrypted in the database and I wanted to decrypt
them. I know one password which is SRSSRS and the encrypted password in the database is
e9830a5640f8ecbf6657f34a1b093f20e1bdd8e0
Can someone tell me how I can decrypt the rest of the passwords ? These encrypted passwords were created by Ruby on Rails project and I am don't know that technology to debug and find out the encryption algorithm or the encryption key

Thanks ...