Personal data encryption implementation for website

Implementing personal data encryption on a website

Personal data encryption in the database is a mandatory element of protection when handling sensitive information. Even if the database is compromised, the attacker gets encrypted data useless without keys.

What and how to encrypt

Data requiring encryption:

• INN, SNILS, passport series/number
• Medical data, diagnoses
• Financial data, card numbers
• Biometrics

Data that should only be hashed (irreversible):

• Passwords → bcrypt, Argon2id
• Secret tokens, API keys

Data requiring searchability:

• Requires deterministic encryption or tokenization

Encryption algorithms

AES-256-GCM — symmetric encryption with authentication. Standard for data at rest encryption.

RSA-OAEP — asymmetric. Used for encrypting symmetric keys.

ChaCha20-Poly1305 — AES alternative on platforms without hardware AES acceleration.

Application-level encryption (Laravel)

class EncryptedCast implements CastsAttributes
{
    public function get($model, string $key, $value, array $attributes): ?string
    {
        if (is_null($value)) return null;
        try {
            return Crypt::decryptString($value);
        } catch (DecryptException) {
            return null;
        }
    }

    public function set($model, string $key, $value, array $attributes): ?string
    {
        if (is_null($value)) return null;
        return Crypt::encryptString($value);
    }
}

class Patient extends Model
{
    protected $casts = [
        'passport_number' => EncryptedCast::class,
        'medical_notes'   => EncryptedCast::class,
        'snils'           => EncryptedCast::class,
    ];
}

$patient->passport_number = '4510 123456';
$decrypted = $patient->passport_number;

Key management

HashiCorp Vault:

$vault = new Vault([
    'address' => 'https://vault.internal:8200',
    'token'   => env('VAULT_TOKEN'),
]);

$keyData = $vault->read('secret/data/app-encryption-key');
$encryptionKey = $keyData['data']['key'];

AWS KMS:

$kms = new KmsClient(['region' => 'eu-west-1']);

$result = $kms->encrypt([
    'KeyId'     => 'arn:aws:kms:eu-west-1:123456:key/abc-123',
    'Plaintext' => $sensitiveData,
]);

$encryptedData = base64_encode($result['CiphertextBlob']);

Envelope Encryption — best practice: data encrypted with Data Encryption Key (DEK), DEK encrypted with Key Encryption Key (KEK), KEK stored in KMS/Vault.

Deterministic encryption for search

Regular AES-GCM generates different ciphertext for same value. Searching encrypted field is impossible. Solutions:

Variant 1: Hash for search + encryption for storage:

class PersonalDataRepository
{
    public function findByPassport(string $passport): ?Patient
    {
        $hash = hash_hmac('sha256', $passport, config('app.search_key'));
        return Patient::where('passport_hash', $hash)->first();
    }

    public function store(string $passport): void
    {
        Patient::create([
            'passport_data' => Crypt::encryptString($passport),
            'passport_hash' => hash_hmac('sha256', $passport, config('app.search_key')),
        ]);
    }
}

Variant 2: PostgreSQL pgcrypto:

INSERT INTO patients (passport)
VALUES (pgp_sym_encrypt('4510 123456', current_setting('app.encryption_key')));

SELECT pgp_sym_decrypt(passport::bytea, current_setting('app.encryption_key'))
FROM patients WHERE id = 1;

Key rotation

class RotateEncryptionKeyCommand extends Command
{
    public function handle(): void
    {
        $oldKey = config('app.old_encryption_key');
        $newKey = config('app.key');

        Patient::chunk(100, function ($patients) use ($oldKey, $newKey) {
            foreach ($patients as $patient) {
                $decrypted = Crypt::decryptString($patient->getRawOriginal('passport_number'));
                $patient->updateQuietly([
                    'passport_number' => Crypt::encryptString($decrypted),
                ]);
            }
        });
    }
}

File encryption

class EncryptedFileStorage
{
    public function store(UploadedFile $file): string
    {
        $content = file_get_contents($file->getPathname());
        $encrypted = Crypt::encrypt($content);

        $path = 'encrypted/' . Str::uuid() . '.enc';
        Storage::put($path, $encrypted);

        return $path;
    }

    public function retrieve(string $path): string
    {
        $encrypted = Storage::get($path);
        return Crypt::decrypt($encrypted);
    }
}

Implementation Timeline

• Encryption on model level (Cast) for main fields: 2–3 days
• Vault/KMS integration + envelope encryption: 5–7 days
• Deterministic encryption + search: +3 days
• Key rotation + access audit: +2–3 days