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

import nacl from '../../deps/nacl-fast.js'
import Base58 from '../../deps/Base58.js'
import ed2curve from '../../deps/ed2curve.js'
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
	}
	return new TextDecoder('utf-8').decode(_decryptedMessage)


}