Encryption
The application supports end-to-end encryption by encrypting message text and recipients' phone numbers before sending them to the API and decrypting them on the device. This ensures that no one – including us as the service provider, the hosting provider, or any third parties – can access the content and recipients of the messages.
Please note that using encryption will increase device battery usage.
Requirements
- Fields
messageand every value in thephoneNumbersfield must be encrypted. - The
isEncryptedfield of the message object must be set totrue. - On the device, the same passphrase must be specified as in step 1.
Algorithm
- Select a passphrase that will be used for encryption and specify it on the device.
- Generate a random salt, with 16 bytes being the recommended size.
- Create a secret key using the PBKDF2 algorithm with SHA1 hash function, key size of 256 bits, and recommended iteration count of 75,000.
- Encrypt the message text and recipients' phone numbers using the AES-256-CBC algorithm and encode the result as Base64.
- Format result as
$aes-256-cbc/pbkdf2-sha1$i=<iteration count>$<base64 encoded salt>$<base 64 encoded encrypted data>. The format is inspired by PHC.
Or use one of the following realization:
PHP
<?php
class Encryptor {
protected string $passphrase;
protected int $iterationCount;
/**
* Encryptor constructor.
* @param string $passphrase Passphrase to use for encryption
* @param int $iterationCount Iteration count
*/
public function __construct(
string $passphrase,
int $iterationCount = 75000
) {
$this->passphrase = $passphrase;
$this->iterationCount = $iterationCount;
}
public function Encrypt(string $data): string {
$salt = $this->generateSalt();
$secretKey = $this->generateSecretKeyFromPassphrase($this->passphrase, $salt, 32, $this->iterationCount);
return sprintf(
'$aes-256-cbc/pbkdf2-sha1$i=%d$%s$%s',
$this->iterationCount,
base64_encode($salt),
openssl_encrypt($data, 'aes-256-cbc', $secretKey, 0, $salt)
);
}
public function Decrypt(string $data): string {
list($_, $algo, $paramsStr, $saltBase64, $encryptedBase64) = explode('$', $data);
if ($algo !== 'aes-256-cbc/pbkdf2-sha1') {
throw new \RuntimeException('Unsupported algorithm');
}
$params = $this->parseParams($paramsStr);
if (empty($params['i'])) {
throw new \RuntimeException('Missing iteration count');
}
$salt = base64_decode($saltBase64);
$secretKey = $this->generateSecretKeyFromPassphrase($this->passphrase, $salt, 32, intval($params['i']));
return openssl_decrypt($encryptedBase64, 'aes-256-cbc', $secretKey, 0, $salt);
}
protected function generateSalt(int $size = 16): string {
return random_bytes($size);
}
protected function generateSecretKeyFromPassphrase(
string $passphrase,
string $salt,
int $keyLength = 32,
int $iterationCount = 300000
): string {
return hash_pbkdf2('sha1', $passphrase, $salt, $iterationCount, $keyLength, true);
}
/**
* @return array<string, string>
*/
protected function parseParams(string $params): array {
$keyValuePairs = explode(',', $params);
$result = [];
foreach ($keyValuePairs as $pair) {
list($key, $value) = explode('=', $pair, 2);
$result[$key] = $value;
}
return $result;
}
}
TypeScript
Please note, that Bun's implementation of crypto package is not optimized, so it is much slower than Node's implementation.
import crypto from "crypto";
class Encryptor {
constructor(protected readonly passphrase: string, protected readonly iterations: number = 75_000) {
}
public Decrypt(input: string): string {
const parts = input.split("$");
if (parts.length !== 5) {
throw new Error("Invalid encrypted text");
}
if (parts[1] !== "aes-256-cbc/pbkdf2-sha1") {
throw new Error("Unsupported algorithm");
}
const paramsStr = parts[2];
const params = this.parseParams(paramsStr);
if (!params.has("i")) {
throw new Error("Missing iteration count");
}
const iterations = parseInt(params.get("i")!);
const salt = Buffer.from(parts[3], "base64");
const encryptedText = Buffer.from(parts[4], "base64");
const secretKey = this.generateSecretKeyFromPassphrase(this.passphrase, salt, 32, iterations);
const decryptedText = this.decryptString(encryptedText, secretKey, salt);
return decryptedText.toString("utf8");
}
protected parseParams(params: string): Map<string, string> {
const keyValuePairs = params.split(",");
const result = new Map<string, string>();
keyValuePairs.forEach(pair => {
const [key, value] = pair.split("=");
result.set(key, value);
});
return result;
}
protected decryptString(input: Buffer, secretKey: Buffer, iv: Buffer): Buffer {
const decipher = crypto
.createDecipheriv("aes-256-cbc", secretKey, iv);
return Buffer.concat([decipher.update(input), decipher.final()]);
}
public Encrypt(input: string): string {
const salt = this.generateSalt();
const secretKey = this.generateSecretKeyFromPassphrase(this.passphrase, salt, 32, this.iterations);
const encryptedText = this.encryptString(Buffer.from(input, "utf8"), secretKey, salt);
return `$aes-256-cbc/pbkdf2-sha1$i=${this.iterations}$${salt.toString("base64")}$${encryptedText.toString("base64")}`;
}
protected encryptString(input: Buffer, secretKey: Buffer, iv: Buffer): Buffer {
const cypher = crypto
.createCipheriv("aes-256-cbc", secretKey, iv);
return Buffer.concat([cypher.update(input), cypher.final()]);
}
protected generateSalt(size: number = 16): Buffer {
return crypto.randomBytes(size);
}
protected generateSecretKeyFromPassphrase(passphrase: string, salt: Buffer, keyLength: number = 32, iterations: number = 75_000): Buffer {
return crypto.pbkdf2Sync(passphrase, salt, iterations, keyLength, "sha1");
}
}
Python
Based on pycryptodome
from Crypto.Cipher import AES
from Crypto.Hash import SHA1
from Crypto.Protocol.KDF import PBKDF2
from Crypto.Random import get_random_bytes
from Crypto.Util.Padding import pad, unpad
class AESEncryptor(BaseEncryptor):
def encrypt(self, cleartext: str) -> str:
saltBytes = self._generate_salt()
key = self._generate_key(saltBytes, self.iterations)
cipher = AES.new(key, AES.MODE_CBC, iv=saltBytes)
encrypted_bytes = cipher.encrypt(pad(cleartext.encode(), AES.block_size))
salt = base64.b64encode(saltBytes).decode("utf-8")
encrypted = base64.b64encode(encrypted_bytes).decode("utf-8")
return f"$aes-256-cbc/pbkdf2-sha1$i={self.iterations}${salt}${encrypted}"
def decrypt(self, encrypted: str) -> str:
chunks = encrypted.split("$")
if len(chunks) < 5:
raise ValueError("Invalid encryption format")
if chunks[1] != "aes-256-cbc/pbkdf2-sha1":
raise ValueError("Unsupported algorithm")
params = self._parse_params(chunks[2])
if "i" not in params:
raise ValueError("Missing iteration count")
iterations = int(params["i"])
salt = base64.b64decode(chunks[-2])
encrypted_bytes = base64.b64decode(chunks[-1])
key = self._generate_key(salt, iterations)
cipher = AES.new(key, AES.MODE_CBC, iv=salt)
decrypted_bytes = unpad(cipher.decrypt(encrypted_bytes), AES.block_size)
return decrypted_bytes.decode("utf-8")
def _generate_salt(self) -> bytes:
return get_random_bytes(16)
def _generate_key(self, salt: bytes, iterations: int) -> bytes:
return PBKDF2(
self.passphrase,
salt,
count=iterations,
dkLen=32,
hmac_hash_module=SHA1,
)
def _parse_params(self, params: str) -> t.Dict[str, str]:
return {k: v for k, v in [p.split("=") for p in params.split(",")]}