How to get tezos KT address from the public key?

Question

In tezos, I am able to get the tezos address starts with tz1 from the public key but I am unable to get the correct KT address. 

I am using this code from github.https://github.com/TezTech/eztz/blob/master/src/main.js#L768 

What is operationHash and ind? there is no comment to explain this.  Is operationHash publicKey in edpk format or some other hashing?

  hash : function(operationHash, ind){
    var ob = utility.b58cdecode(operationHash, prefix.o), tt = [], i=0;
    for(; i<ob.length; i++){
      tt.push(ob[i]);
    }
    tt = tt.concat([
     (ind & 0xff000000) >> 24,
     (ind & 0x00ff0000) >> 16,
     (ind & 0x0000ff00) >> 8,
     (ind & 0x000000ff)
    ]);
    return utility.b58cencode(library.sodium.crypto_generichash(20, new Uint8Array(tt)), prefix.KT);
  },

Is there any npm package available which do this?

Thanks

Answer 1

KT addresses are the addresses of smart contract (aka. "originated accounts"). Contrary to tz addresses (aka. "implicit accounts"), smart contracts are not associated with a pair of cryptographic keys because there is no secret place at which they could store a secret key.

As the name "originated account" suggests, the existence of a smart contract starts at its origination operation. More precisely, the KT address is derived from the hash of the origination operation and a simple counter (ind in the code you quote, it is called "origination index" in the code of the protocol file contract_repr.ml) that guarantees that several smart contracts originated in the same operation have distinct addresses.

Here is the documentation from the protocol (file contract_repr.mli):

Originated contracts handles are crafted from the hash of the operation that triggered their origination (and nothing else). As a single operation can trigger several originations, the corresponding handles are forged from a deterministic sequence of nonces, initialized with the hash of the operation.