Compare Encrpted Password

Hi I am new to Encrypting password.I have to comapre Encrypted password with string password that user enters thru UI I dont know what mechanism is used for encrypting the password in DB..It was developed my someoneelse. Only clue I have is when i enter string as reena it encrypted to lgMw8kaPYfhhkL/cMMiX+wA= and when i enter string  aan it encrypted to zZwJfo4+uGoA
I have to compare the string in the ui with db password..pls advise
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