Encryption in smartpy tezos

Question

I wanted to give encryption to a string before storing it in smart contract.

For example I have "hello" its 256 equivalent should be "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"

Please note that both input and output should be of type sp.TString

Below is a failed attempt to do so. It will help you understand what I am trying to do.

import smartpy as sp
class Try(sp.Contract):
    def __init__(self):
        self.init(mystr = sp.string(""))

    @sp.entry_point
    def encypt(self,params):
        self.data.mystr =  sp.sha256(params.key)


@sp.add_test(name="try")
def test():
    obj = Try()
    scenario = sp.test_scenario()
    scenario += obj
    scenario += obj.encypt(key="hello")

Thanks in advance.

Answer 1

Both the input and output of a hash function is a bytes in Michelson.

There is a hack for the input, you can do something like that.

import smartpy as sp

class MyContract(sp.Contract):
    def __init__(self):
        self.init(x = sp.sha256(sp.slice(sp.pack("hello"), 6, 5).open_some()))

@sp.add_test(name = "")
def test():
    scenario = sp.test_scenario()
    c1 = MyContract()
    scenario += c1

https://smartpy.io/demo/index.html?code=eJxVT7sKwzAM3P0VIpNFS6CFZigECp37DUY4CjF1bGN5aP6@dh_Qajrdne6QW1PMBWSlXNIGJCBJKetJBG7bNYaSyRYtqf9iPCuoM_EMxrjgijFa2M8fvk1b@ybpB4w1sJeFjqehpYh3lhtIZO@6W9j72OEehj2csI@Jg5G4skZEpS7VR9NkCkvRgVauaV2HqnW_uE@nWA6UXXyXNcV8KY0vhz1U7ecf_L_bjdWhnvd1Upo-

You can write another hack for the output as well. Do we really need this?