120 lines
5.2 KiB
Swift
120 lines
5.2 KiB
Swift
//
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// CryptoChatModelMsg.swift
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// PayCash
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//
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// Created by Saveliy Stavitsky on 8/17/20.
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// Copyright © 2020 List. All rights reserved.
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//
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import Foundation
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import CryptoSwift
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extension CryptoChat.Model {
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struct Msg: Codable {
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let from: String
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let to: String
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let iv: String
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let ephemPublicKey: String
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let cipherText: String
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let mac: String
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private enum CodingKeys: String, CodingKey {
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case from
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case to
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case iv
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case ephemPublicKey = "ephem_key"
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case cipherText = "cipher_text"
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case mac
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}
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let curve = uECC_secp256k1()
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init(from: String, to: String, iv: String, ephemPublicKey: String, cipherText: String, mac: String) {
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self.from = from
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self.to = to
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self.iv = iv
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self.ephemPublicKey = ephemPublicKey
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self.cipherText = cipherText
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self.mac = mac
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}
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//Encrypt
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init(from: String, to: String, msg: String, receiverPublicKey: String) throws {
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self.from = from
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self.to = to
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//Read end decompress receiver public key into bytes array for future use in alg
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let receiverPublicKeyCompressed = try Data(eosioPublicKey: receiverPublicKey).bytes
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var receiverPublicKeyDecompressed = Array(repeating: UInt8(0), count: 64)
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uECC_decompress(receiverPublicKeyCompressed, &receiverPublicKeyDecompressed, curve)
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//Generate ephem public and private key pair into bytes array
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var ephemPublicKey = Array(repeating: UInt8(0), count: Int(uECC_curve_public_key_size(curve)) * 2)
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var ephemPrivateKey = Array(repeating: UInt8(0), count: Int(uECC_curve_private_key_size(curve)))
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uECC_make_key(&ephemPublicKey, &ephemPrivateKey, curve)
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ephemPublicKey = Data(bytes: ephemPublicKey, count: Int(uECC_curve_public_key_size(curve))).bytes
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//Calculate symetric shared key for encryption
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var sharedKey = Array(repeating: UInt8(0), count: 32)
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uECC_shared_secret(receiverPublicKeyDecompressed, ephemPrivateKey, &sharedKey, curve)
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//Calculate sharedKey sha512 (64 bytes) and split it to encryptionKey - first 32 bytes and macKey - second 32 bytes
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let hash = sharedKey.sha512()
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let encryptionKey = [UInt8](hash[..<32])
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let macKey = [UInt8](hash[32...])
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//Generate iv random 16 bytes
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let iv = (0..<16).map({ _ in UInt8.random(in: 0..<UInt8.max) })
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//Encrypt msg with encryptionKey and iv
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let ciphertext = try AES(key: encryptionKey, blockMode: CBC(iv: iv), padding: .pkcs7).encrypt(msg.bytes)
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//Calculate HMAC for msg validation
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let compressedEphemPublicKey = ([4] + ephemPublicKey).toData().toCompressedPublicKey ?? Data()
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let dataToMac = iv + compressedEphemPublicKey.bytes + ciphertext
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let mac = try HMAC(key: macKey, variant: .sha256).authenticate(dataToMac)
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self.iv = iv.toHexString()
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self.ephemPublicKey = compressedEphemPublicKey.toEosioK1PublicKey
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self.cipherText = ciphertext.toHexString()
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self.mac = mac.toHexString()
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}
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func decrypt(privateKey: String) throws -> String {
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let privateKeyBytes = try Data(eosioPrivateKey: privateKey).bytes
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//Read end decompress ephem public key into bytes array for future use in alg
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let compressedEphemPublicKey = try Data(eosioPublicKey: self.ephemPublicKey).bytes
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var decompressedEphemPublicKey = Array(repeating: UInt8(0), count: 64)
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uECC_decompress(compressedEphemPublicKey, &decompressedEphemPublicKey, curve)
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//Calculate symetric shared key for encryption
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var sharedKey = Array(repeating: UInt8(0), count: 32)
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uECC_shared_secret(decompressedEphemPublicKey, privateKeyBytes, &sharedKey, curve)
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//Calculate sharedKey sha512 (64 bytes) and split it to encryptionKey - first 32 bytes and macKey - second 32 bytes
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let hash = sharedKey.sha512()
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let encryptionKey = [UInt8](hash[..<32])
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let macKey = [UInt8](hash[32...])
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//Calculate HMAC for msg validation
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if let ivBytes = Data(hexString: iv)?.bytes,
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let cipherTextBytes = Data(hexString: cipherText)?.bytes {
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let dataToMac = ivBytes + compressedEphemPublicKey + cipherTextBytes
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let realMac = try HMAC(key: macKey, variant: .sha256).authenticate(dataToMac)
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if (realMac.toHexString().uppercased() == mac.uppercased()) {
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let plaintext = try AES(key: encryptionKey, blockMode: CBC(iv: ivBytes), padding: .pkcs7).decrypt(cipherTextBytes)
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return String(bytes: plaintext, encoding: .utf8)
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?? "<plaintext>*** Wrong message encryption format ***</plaintext>"
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} else {
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return "<plaintext>\(L10n.CryptoChat.Chats.decodeError)</plaintext>"
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}
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}
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return "<plaintext>*** Wrong iv or cipherText hex format ***</plaintext>"
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}
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}
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}
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