How decrypt keccak algorithm [closed]

Question

I am preparing a presentation about Keccak (http://keccak.noekeon.org/).

In that presentation, I would like to encrypt a plain-text – which brings up the following questions:

1. What is the exact role of the padding function (how do we obtain a cube of 1600 bits from 64 bit)?
2. After encrypting the text, how can we decrypt it again?

Answer 1

You cannot "decrypt" the output of Keccak, since it isn't an encryption algorithm, but a one way hash function. Instead, you use it for verifying that a hash value is indeed the hash output of a particular text (which you must know already), simply by calculating the hash of the text, and comparing the output to the first hash value.