MongoDB Academy · Ders

İstemci Tarafında Alan Düzeyinde Şifreleme

İstemci Tarafında Alan Düzeyinde Şifreleme, CoddyKit'te ücretsiz bir MongoDB Academy dersidir. Bu, 4 dersinin 4. dersidir. Aşağıdan dersin tamamını ücretsiz okuyabilir, sonra tarayıcıda yerleşik kod editörü ve 7/24 yapay zeka koçu ile uygulamalı olarak pratik yapabilirsin. Bu, MongoDB Academy öğrenme yolunun bir parçasıdır ve ilerlemeniz web ve CoddyKit uygulaması arasında senkronize olur. MongoDB Academy kursu toplamda 4 dersten oluşur.

Bu dersin bazı bölümleri henüz çevrilmemiş olup İngilizce olarak gösterilmektedir.

Why Field-Level Encryption?

Even with TLS and encryption at rest, the MongoDB server sees plaintext data once it is decrypted from disk. A compromised DBA account, a rogue cloud engineer with disk access, or a database backup leak could expose sensitive fields. Client-Side Field Level Encryption (CSFLE) solves this by encrypting individual sensitive fields — like SSNs, credit card numbers, or health data — inside the client driver, before the data ever reaches the server. The server only ever stores ciphertext.

How CSFLE Works at a High Level

CSFLE uses two layers of keys. The Customer Master Key (CMK) is stored in an external Key Management System (AWS KMS, Azure Key Vault, GCP KMS, or a local key). The CMK encrypts a Data Encryption Key (DEK), which is stored in a MongoDB collection called the Key Vault. The driver fetches and decrypts the DEK using the CMK at query time, then uses the DEK to encrypt/decrypt individual field values. The server never sees the CMK or the DEK in plaintext.

Two Modes: Automatic and Explicit

CSFLE offers two encryption modes. Automatic CSFLE (requires MongoDB Enterprise or Atlas) encrypts and decrypts fields transparently based on a JSON schema — your application code does not change. Explicit (Manual) CSFLE is available in the Community driver and requires the application to call encrypt/decrypt methods explicitly. Automatic is far more convenient for new projects; explicit gives maximum control over which fields are encrypted per operation.

Setting Up the Key Vault Collection

Before encrypting any data, create a Key Vault collection — a special MongoDB collection that stores Data Encryption Keys. The key vault is just a regular collection (e.g., encryption.__keyVault) but it must have a unique index on the keyAltNames field. DEKs are stored as BSON documents with the key material encrypted by your CMK — even the key vault only stores ciphertext.

const { MongoClient, ClientEncryption } = require('mongodb-client-encryption')

// Step 1: Create key vault collection with unique index
const client = new MongoClient('mongodb://localhost:27017')
await client.connect()

const keyVaultColl = client.db('encryption').collection('__keyVault')
await keyVaultColl.createIndex(
  { keyAltNames: 1 },
  { unique: true, partialFilterExpression: { keyAltNames: { $exists: true } } }
)

Creating a Data Encryption Key

Use the ClientEncryption helper to create a DEK. The key is encrypted by your CMK (here a local master key for development) and stored in the key vault. In production, replace the local provider with aws, azure, or gcp and provide the KMS credentials. You can create multiple DEKs — for example, one per tenant in a multi-tenant application.

const crypto = require('crypto')

// 96-byte local master key (development only — use KMS in production)
const localMasterKey = crypto.randomBytes(96)

const encryption = new ClientEncryption(client, {
  keyVaultNamespace: 'encryption.__keyVault',
  kmsProviders: { local: { key: localMasterKey } }
})

// Create a DEK with an alias for easy reference
const dataKey = await encryption.createDataKey('local', {
  keyAltNames: ['userSensitiveDataKey']
})
console.log('DEK id:', dataKey)

Defining the Encrypted Fields Schema

For automatic CSFLE, define an encrypted fields map that tells the driver which fields to encrypt and with which algorithm. AEAD_AES_256_CBC_HMAC_SHA_512-Deterministic produces the same ciphertext for the same plaintext — enabling equality queries on encrypted fields. AEAD_AES_256_CBC_HMAC_SHA_512-Random produces different ciphertext each time — stronger but not queryable.

const encryptedFieldsMap = {
  'myApp.users': {
    fields: [
      {
        path: 'ssn',
        bsonType: 'string',
        // Deterministic: can query encrypted SSN with equality
        algorithm: 'AEAD_AES_256_CBC_HMAC_SHA_512-Deterministic',
        keyId: dataKey
      },
      {
        path: 'creditCardNumber',
        bsonType: 'string',
        // Random: cannot query, but stronger encryption
        algorithm: 'AEAD_AES_256_CBC_HMAC_SHA_512-Random',
        keyId: dataKey
      }
    ]
  }
}

Creating an Auto-CSFLE MongoClient

To enable automatic CSFLE, configure the MongoClient with the autoEncryption option, providing the key vault namespace, KMS credentials, and the encrypted fields map. The driver will automatically encrypt matching fields on insert/update and decrypt them on read. No changes to your application queries are required.

const secureClient = new MongoClient('mongodb://localhost:27017', {
  autoEncryption: {
    keyVaultNamespace: 'encryption.__keyVault',
    kmsProviders: { local: { key: localMasterKey } },
    encryptedFieldsMap: encryptedFieldsMap
  }
})

await secureClient.connect()
const users = secureClient.db('myApp').collection('users')

// SSN and creditCardNumber are auto-encrypted on insert
await users.insertOne({
  name: 'Alice',
  ssn: '123-45-6789',           // encrypted transparently
  creditCardNumber: '4111-1111-1111-1111'  // encrypted transparently
})

Querying Encrypted Fields

With deterministic encryption, you can perform equality queries on encrypted fields — the driver encrypts the query value with the same DEK before sending it to the server, so the server compares ciphertexts. With random encryption, equality queries are not possible because the same plaintext produces different ciphertexts each time. Range and regex queries are not supported on encrypted fields in CSFLE.

// Query an encrypted SSN field (deterministic encryption)
// The driver auto-encrypts '123-45-6789' before sending the query
const user = await users.findOne({ ssn: '123-45-6789' })

// The result has SSN decrypted automatically by the driver:
console.log(user.ssn)  // '123-45-6789' (decrypted)

// A client WITHOUT the key sees ciphertext:
// user.ssn = Binary(Buffer.from('...'), 6)  // encrypted blob

Explicit Encryption With the Driver API

Explicit CSFLE gives you per-operation control. Call encryption.encrypt() before inserting and encryption.decrypt() after reading. This works in Community edition drivers without requiring the automatic CSFLE shared library. It is more verbose but gives complete flexibility — you can encrypt different fields in different documents with different DEKs.

// Explicit encryption
const encryptedSsn = await encryption.encrypt('123-45-6789', {
  algorithm: 'AEAD_AES_256_CBC_HMAC_SHA_512-Deterministic',
  keyAltName: 'userSensitiveDataKey'
})

await users.insertOne({
  name: 'Bob',
  ssn: encryptedSsn  // manually encrypted Binary value
})

// Explicit decryption
const doc = await users.findOne({ name: 'Bob' })
const decryptedSsn = await encryption.decrypt(doc.ssn)
console.log(decryptedSsn)  // '123-45-6789'

Key Rotation for Field-Level Encryption

Rotate DEKs periodically to limit the exposure window if a key is compromised. Key rotation in CSFLE involves creating a new DEK, re-encrypting all documents that use the old DEK (field by field), and then deleting the old DEK from the key vault. This process can be done as a background migration script without downtime. Rotating CMKs in KMS (wrapping the DEK) does not require touching the encrypted documents at all.

CSFLE Limitations and Considerations

CSFLE has important limitations to plan for: no server-side operations on encrypted fields (aggregation, sorting, and range queries on encrypted fields are not supported, except equality on deterministic fields); schema changes require DEK re-use or re-encryption; automatic CSFLE requires MongoDB Enterprise or Atlas; and performance overhead from encryption/decryption in the driver adds latency. Design your data model to minimise which fields need encryption.

Quick Check

Test your understanding of MongoDB & NoSQL Databases concepts from this lesson.

Lesson Recap

In this lesson you learned: CSFLE encrypts sensitive fields inside the driver before data reaches the server, so even MongoDB itself only sees ciphertext, deterministic encryption enables equality queries while random encryption provides stronger security without queryability, and the two-tier key model (CMK in KMS wrapping DEK in key vault) keeps encryption keys outside MongoDB. Next up we explore MongoDB schema design patterns.

Sıkça Sorulan Sorular

“İstemci Tarafında Alan Düzeyinde Şifreleme” dersi ücretsiz mi?

Evet — “İstemci Tarafında Alan Düzeyinde Şifreleme” dersin tüm metni burada web'de ücretsiz olarak okunabilir. Etkileşimli olarak pratik yapmak (yerleşik kod editörü ve 7/24 yapay zeka koçu) ve MongoDB Academy kursunun geri kalanını açmak için CoddyKit PRO'ya yükselt. MongoDB Academy kursu toplamda 4 dersten oluşur.

“İstemci Tarafında Alan Düzeyinde Şifreleme” dersinde ne öğreneceğim?

Öğrenenler, hassas alanları uygulamadan çıkmadan önce şifrelemek ve düz metnin sunucuya ulaşmasını önlemek için MongoDB'nin İstemci Tarafında Alan Düzeyinde Şifreleme özelliğini yapılandıracaktır. MongoDB Academy ile uygulamalı kodu tarayıcıda doğrudan çalıştırarak pratik yaparsın ve 7/24 yapay zeka koçu dersi çalışırken sorularını yanıtlar.

MongoDB Academy öğrenmeye başlamak için deneyim gerekli mi?

Önceden deneyim gerekmez. CoddyKit'te MongoDB Academy, başlangıçtan ileri seviyeye kadar yapılandırıldığı için buradan başlayabilir veya başından başlayıp kendi hızında ilerleme yapabilirsin. Bu, 4 dersinin 4. dersidir.

“İstemci Tarafında Alan Düzeyinde Şifreleme” dersi ne kadar sürer?

Çoğu CoddyKit dersi yaklaşık 5–10 dakika sürer. Her biri kısa ve etkileşimli olduğu için sabit ilerleme yaparsın ve web ile uygulama arasında tam olarak bıraktığın yerden devam edebilirsin.

Bu MongoDB Academy dersinde kod yazıp çalıştırabilir miyim?

Evet. Her MongoDB Academy dersi yerleşik bir kod editörü içerir, bu sayede tarayıcıda gerçek kod yazıp çalıştırabilir ve anlık yapay zeka geri bildirimi alırsın — yerel kurulum gerekli değildir.

Bu kursun tüm dersleri

Kimlik Doğrulama Mekanizmaları: SCRAM ve x.509
Rol Tabanlı Erişim Denetimi: Yerleşik ve Özel Roller
Beklemede Şifreleme ve Aktarım Sırasında TLS
İstemci Tarafında Alan Düzeyinde Şifreleme

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