encryption

Field-Level Encryption Example

Encrypt PII at rest, decrypt transparently on load, and crypto-shred per tenant for GDPR erasure.

Event stores keep every change forever, so any PII written today lives in your history indefinitely — that is a compliance liability unless it is protected. go-mink encrypts individual event fields (email, phone) with envelope encryption while leaving other fields (name, country) as plaintext so they stay queryable. Because each tenant has its own key, revoking a key permanently destroys that tenant's data — satisfying the GDPR "right to erasure" without rewriting immutable events.

What this demonstrates

• Field-level encryption — WithEncryptedFields("CustomerCreated", "email", "phone") encrypts only the named fields; name and country remain plaintext and queryable.
• Transparent decryption — LoadAggregate / Load decrypt automatically, so domain code never sees ciphertext.
• Per-tenant keys — WithTenantKeyResolver maps each event's Metadata.TenantID to a key ID, isolating tenants cryptographically.
• Crypto-shredding — provider.RevokeKey("tenant-B") makes that tenant's data permanently unrecoverable (GDPR right to erasure), while other tenants stay readable.
• Graceful degradation — WithDecryptionErrorHandler catches encryption.ErrKeyRevoked and returns the still-encrypted payload instead of failing the load.

Running

go run ./examples/encryption

No infrastructure required — encryption keys and the event store are in-memory (local.New + memory.NewAdapter).

What happens

1. Two random 32-byte keys are generated and registered with a local provider as tenant-A and tenant-B. A FieldEncryptionConfig marks email and phone on CustomerCreated as encrypted.
2. Encrypt on save, decrypt on load — a customer is saved with the tenant-A key. LoadRaw prints the ciphertext at rest plus the encrypted-field list and key ID from metadata, then LoadAggregate prints the fully decrypted name, email, and phone.
3. Per-tenant keys — a second customer is appended with Metadata{TenantID: "B"}. The resolver picks tenant-B; the printed key ID confirms it, and Load returns the decrypted email.
4. Crypto-shredding — provider.RevokeKey("tenant-B") is called. Reloading tenant B's event triggers the decryption-error handler, which prints [SHREDDED] and leaves the email encrypted.
5. Isolation — tenant A's customer is loaded one last time and still decrypts normally, proving revocation only affected tenant B.

Key APIs

• mink.NewFieldEncryptionConfig(...) — build the encryption config from options.
• mink.WithEncryptionProvider(provider) — supply the key provider that performs envelope encryption.
• mink.WithDefaultKeyID("tenant-A") — key used when no tenant-specific key is resolved.
• mink.WithEncryptedFields(eventType, fields...) — declare which fields on an event type are encrypted.
• mink.WithTenantKeyResolver(func(tenantID) string) — derive a key ID from each event's tenant.
• mink.WithDecryptionErrorHandler(func(err, eventType, metadata) error) — decide what happens when decryption fails (e.g. after key revocation).
• mink.WithFieldEncryption(encConfig) — attach the config to the event store via mink.New.
• mink.GetEncryptedFields(metadata) / mink.GetEncryptionKeyID(metadata) — read encryption metadata off a stored event.
• local.New(local.WithKey(...)) — in-memory AES-256-GCM provider; returns (*Provider, error).
• provider.RevokeKey(keyID) — crypto-shred: destroy a key so its data can no longer be decrypted.

Related

• Examples: export · full-ecommerce
• Docs: Security · API reference