Adhiraj Singh
57 lines
1.4 KiB
TypeScript
57 lines
1.4 KiB
TypeScript
import { hkdf } from './crypto'
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/**
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* LT Hash is a summation based hash algorithm that maintains the integrity of a piece of data
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* over a series of mutations. You can add/remove mutations and it'll return a hash equal to
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* if the same series of mutations was made sequentially.
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*/
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const o = 128;
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class d {
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salt: string
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constructor(e: string) {
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this.salt = e
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}
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add(e, t) {
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var r = this;
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for(const item of t) {
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e = r._addSingle(e, item)
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}
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return e
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}
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subtract(e, t) {
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var r = this;
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for(const item of t) {
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e = r._subtractSingle(e, item)
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}
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return e
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}
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subtractThenAdd(e, t, r) {
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var n = this;
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return n.add(n.subtract(e, r), t)
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}
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_addSingle(e, t) {
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var r = this;
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const n = new Uint8Array(hkdf(Buffer.from(t), o, { info: r.salt })).buffer;
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return r.performPointwiseWithOverflow(e, n, ((e,t)=>e + t))
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}
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_subtractSingle(e, t) {
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var r = this;
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const n = new Uint8Array(hkdf(Buffer.from(t), o, { info: r.salt })).buffer;
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return r.performPointwiseWithOverflow(e, n, ((e,t)=>e - t))
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}
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performPointwiseWithOverflow(e, t, r) {
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const n = new DataView(e)
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, i = new DataView(t)
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, a = new ArrayBuffer(n.byteLength)
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, s = new DataView(a);
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for (let e = 0; e < n.byteLength; e += 2)
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s.setUint16(e, r(n.getUint16(e, !0), i.getUint16(e, !0)), !0);
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return a
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}
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}
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export const LT_HASH_ANTI_TAMPERING = new d('WhatsApp Patch Integrity') |