Crate cqrs_es_crypto 

cqrs-es-crypto — transparent PII encryption and GDPR crypto-shredding for [cqrs-es].

Overview

This crate wraps any cqrs_es::persist::PersistedEventRepository with a crypto-shredding layer that:

• Encrypts PII fields in designated event types on the write path using AES-256-GCM, keyed by a per-subject Data Encryption Key (DEK).
• Decrypts PII fields transparently on the read path when the DEK is present.
• Redacts PII fields when the DEK has been deleted (crypto-shredded), making the data permanently irrecoverable without touching individual events.

Which event types carry PII, and how their payloads are structured, is defined by the caller through the PiiEventCodec trait. The crate itself has no knowledge of any particular domain or event schema.

Known limitations

• stream_all_events is not supported: CryptoShreddingEventRepository returns an error if called, because the cqrs_es::persist::ReplayStream API does not expose raw cqrs_es::persist::SerializedEvent items for interception. Use [CryptoShreddingEventRepository::get_events] or [CryptoShreddingEventRepository::stream_events] per aggregate instead.
• Snapshots are not encrypted. If your aggregate state contains PII, snapshots will store it in plaintext and crypto-shredding will not redact it.

Key management

Each subject gets a unique DEK wrapped by a Key Encryption Key (KEK) via StaticKekProvider (env-var backed) or any KekProvider implementation. [PostgresKeyStore] persists wrapped DEKs in subject_encryption_keys. Deleting a row is the shredding operation. The kek_id column records which KEK version wrapped each DEK, enabling zero-downtime KEK rotation.

The required DDL is:

CREATE TABLE subject_encryption_keys (
    key_id       UUID      NOT NULL PRIMARY KEY DEFAULT gen_random_uuid(),
    subject_id   UUID      NOT NULL UNIQUE,
    wrapped_key  BYTEA     NOT NULL,
    kek_id       TEXT      NOT NULL,
    rewrapped_at TIMESTAMP,
    created_at   TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);
CREATE INDEX ON subject_encryption_keys (kek_id);

Usage

use std::sync::Arc;
use cqrs_es_crypto::{
    CryptoShreddingEventRepository, EncryptedPiiSentinel, FieldCipher,
    PiiEventCodec, PiiFields, PostgresKeyStore, StaticKekProvider,
};

// 1. Implement PiiEventCodec for your domain.
struct MyCodec;
impl PiiEventCodec for MyCodec { /* ... */ }

// 2. Build the crypto repository around your inner repository.
let provider = Arc::new(StaticKekProvider::single("v1", kek_bytes)?);
let key_store = Arc::new(PostgresKeyStore::new(pool.clone(), Arc::clone(&provider)));
let codec = Arc::new(MyCodec);
let repo = CryptoShreddingEventRepository::new(
    inner_repo, key_store, FieldCipher::new(), codec,
);

Cargo features

• derive: enables #[derive(PiiCodec)] from cqrs-es-crypto-derive.
• chrono: implies derive; teaches the derive macro to redact chrono::NaiveDate secret fields to "0000-01-01" by default. Per-field overrides are available via #[pii(secret, redact = "...")]. See the derive crate’s docs.
• testing: exposes [InMemoryEventRepository] for downstream tests.

Re-exports

pub use cipher::CryptoError;

pub use cipher::EncryptedPayload;

pub use cipher::FieldCipher;

pub use cipher::KeyMaterial;

pub use cipher::PiiCipher;Deprecated

pub use kek::KekError;

pub use kek::KekHandle;

pub use kek::KekProvider;

pub use kek::StaticKekProvider;

pub use kek::WrappedDek;

pub use key_store::InMemoryKeyStore;

pub use key_store::KeyStore;

pub use key_store::KeyStoreError;

pub use rewrap::RewrapStats;

pub use rewrap::RewrapWorker;

pub use rewrap::RewrapWorkerOptions;

pub use repository::CryptoShreddingEventRepository;

pub use repository::EncryptedPiiExtract;

pub use repository::EncryptedPiiSentinel;

pub use repository::PiiEventCodec;

pub use repository::PiiFields;

Modules

cipher

AES-256-GCM field encryption and AES-256-KWP key wrapping for GDPR crypto-shredding.

kek

Key Encryption Key (KEK) provider abstraction for DEK wrap/unwrap.

key_store

Per-subject Data Encryption Key (DEK) management for GDPR crypto-shredding.

repository

Generic transparent PII encryption and GDPR crypto-shredding for cqrs-es.

rewrap

Background worker for re-wrapping DEKs still encrypted under a retired KEK version.