Table of Contents

Hero Sample — Encryption

Concept: [EncryptData] fields stay confidential across tenants by binding the AES-GCM authentication tag to the tenant id as AAD. Cross-tenant decryption fails by cryptography, not by query filtering. The full why lives in the Tenant-Aware Encryption concept page; this is the runnable proof.

What you'll see

  1. TenantAwareEncryptor — AES-256-GCM with one master key and AAD = tenant-id bytes.
  2. Two tenants seal the same SSN — "123-45-6789" is encrypted under tenant A and tenant B. The console prints both ciphertexts (different — fresh nonces every seal).
  3. Same-tenant decryption — each tenant reads its own row back, plaintext recovered.
  4. Cross-tenant attack — taking tenant A's sealed value and trying to decrypt under tenant B raises AuthenticationTagMismatchException (a CryptographicException subclass) because the AAD doesn't match.
  5. Reverse direction — same result. The AAD binding is symmetric.

Running

dotnet run --project samples/Stratara.Sample.Encryption

Expected output (abridged):

=== Stratara Encryption ===

--- Seal the same SSN under two different tenants ---
  Plaintext (both):  '123-45-6789'
  Alice ciphertext:  95DE82D0… (tag AFE936C8…)
  Bob   ciphertext:  33BA0CDF… (tag ACB34420…)

--- Read each customer back under its own tenant context ---
  Alice: '123-45-6789'  (tenant A reads tenant A — OK)
  Bob:   '123-45-6789'  (tenant B reads tenant B — OK)

--- Cross-tenant attack: take Alice's row from the DB, try to decrypt as tenant B ---
  CAUGHT: AuthenticationTagMismatchException — The computed authentication tag did not match the input authentication tag.
  AES-GCM rejected the authentication tag because the AAD (tenant id) does not match.
  This holds even with the correct master key. The tenant binding is mathematical.

How this maps to the real Stratara

Sample Real Stratara
[Encrypted] marker (sample-local) [EncryptData] from Stratara.Abstractions
TenantAwareEncryptor (hardcoded master key) ISecureJsonSerializer (fields) / ISecureBlobEncryptor (streams) backed by an IKeyStore — production EnvelopeFileKeyStore from Stratara.Security, or Key Vault / KMS / HSM
Manual Encrypt / Decrypt calls [EncryptData] at the serialization boundary — transparent on save/load
Tenant id passed explicitly a KeyScope resolved from ISessionContextProvider.Current.TenantId — ambient per request
One master key, AAD-only separation KEK-wrapped, versioned per-KeyScope data-encryption keys on top of the AAD binding

See also

  • Encrypt Sensitive Data — the wire-it-up-in-your-own-host guide (how to register IKeyStore, key rotation considerations, the EncryptionMetadataDriftGuard startup check).

Sister hero sample