qortal-ui/crypto/api/transactions/chat/decryptChatMessage.js

import nacl from '../../deps/nacl-fast'
import Base58 from '../../deps/Base58'
import ed2curve from '../../deps/ed2curve'
import { Sha256 } from 'asmcrypto.js'

export const decryptChatMessage = (encryptedMessage, privateKey, recipientPublicKey, lastReference) => {
	let _encryptedMessage = Base58.decode(encryptedMessage)

	const _base58RecipientPublicKey = recipientPublicKey instanceof Uint8Array ? Base58.encode(recipientPublicKey) : recipientPublicKey
	const _recipientPublicKey = Base58.decode(_base58RecipientPublicKey)
	const _lastReference = lastReference instanceof Uint8Array ? lastReference : Base58.decode(lastReference)
	const convertedPrivateKey = ed2curve.convertSecretKey(privateKey)
	const convertedPublicKey = ed2curve.convertPublicKey(_recipientPublicKey)
	const sharedSecret = new Uint8Array(32)

	nacl.lowlevel.crypto_scalarmult(sharedSecret, convertedPrivateKey, convertedPublicKey)

	const _chatEncryptionSeed = new Sha256().process(sharedSecret).finish().result
	const _decryptedMessage = nacl.secretbox.open(_encryptedMessage, _lastReference.slice(0, 24), _chatEncryptionSeed)

	let decryptedMessage = ''

	_decryptedMessage === false ? decryptedMessage : decryptedMessage = new TextDecoder('utf-8').decode(_decryptedMessage)
	return decryptedMessage
}

export const decryptChatMessageBase64 = (encryptedMessage, privateKey, recipientPublicKey, lastReference) => {
	let _encryptedMessage = atob(encryptedMessage)

	const binaryLength = _encryptedMessage.length
	const bytes = new Uint8Array(binaryLength)

	for (let i = 0; i < binaryLength; i++) {
		bytes[i] = _encryptedMessage.charCodeAt(i)
	}

	const _base58RecipientPublicKey = recipientPublicKey instanceof Uint8Array ? Base58.encode(recipientPublicKey) : recipientPublicKey
	const _recipientPublicKey = Base58.decode(_base58RecipientPublicKey)
	const _lastReference = lastReference instanceof Uint8Array ? lastReference : Base58.decode(lastReference)
	const convertedPrivateKey = ed2curve.convertSecretKey(privateKey)
	const convertedPublicKey = ed2curve.convertPublicKey(_recipientPublicKey)
	const sharedSecret = new Uint8Array(32)

	nacl.lowlevel.crypto_scalarmult(sharedSecret, convertedPrivateKey, convertedPublicKey)

	const _chatEncryptionSeed = new Sha256().process(sharedSecret).finish().result
	const _decryptedMessage = nacl.secretbox.open(bytes, _lastReference.slice(0, 24), _chatEncryptionSeed)

	if (_decryptedMessage === false) {
		return _decryptedMessage
	}

	let decrypted1 = new TextDecoder('utf-8').decode(_decryptedMessage)

	if (decrypted1.includes('messageText')) {
		let decrypted2 = JSON.parse(decrypted1)
		let decrypted3 = Object.assign(decrypted2, {isFrivate: true})
		return JSON.stringify(decrypted3)
	}

	return new TextDecoder('utf-8').decode(_decryptedMessage)
}