def decryptInCBC(key,fileNameToDecrypt,iv,fileNameToSavePT):
    iv = b64decode(iv)
    ct = b64decode(getDataInBytes(fileNameToDecrypt))
    cipher = AES.new(key, AES.MODE_CBC, iv)
    start=timer()
    pt = unpad(cipher.decrypt(ct), AES.block_size)
    end=timer()
    print("Time Taken to Decrypt is ",end-start)
    print("Time Taken to Decrypt per byte is ",(end-start)/len(pt))
    pt=pt.decode("utf-8")
    writeFile(pt,fileNameToSavePT)
    return pt