PostQuantum.FileEncryption.Gcp 1.6.0

PostQuantum.FileEncryption.Gcp

Envelope encryption with Google Cloud KMS — your master key never leaves Google Cloud. GcpKmsContentKeyProvider plugs Cloud KMS into PostQuantum.FileEncryption's IContentKeyProvider seam: every file is encrypted under a fresh per-file content key that Cloud KMS Encrypt wraps under your key-ring key; decryption sends only the small wrapped blob back to Cloud KMS Decrypt.

dotnet add package PostQuantum.FileEncryption.Gcp

Usage

using Google.Cloud.Kms.V1;
using PostQuantum.FileEncryption;
using PostQuantum.FileEncryption.Gcp;

var kms = await KeyManagementServiceClient.CreateAsync();   // credentials from Application Default Credentials
var provider = new GcpKmsContentKeyProvider(kms,
    "projects/my-project/locations/global/keyRings/my-ring/cryptoKeys/my-app-key");

await new PqFileEncryptor().EncryptFileAsync("report.pdf", "report.pdf.pqfe", provider);
await new PqFileDecryptor().DecryptFileAsync("report.pdf.pqfe", "report.pdf", provider);

Optionally bind extra additional authenticated data (required to unwrap):

var provider = new GcpKmsContentKeyProvider(kms, cryptoKeyName,
    Encoding.UTF8.GetBytes("tenant=contoso"));

Security behavior

• The master key stays in Cloud KMS. Cloud KMS has no server-side data-key generation, so the per-file content key is generated locally and crosses the boundary once, for wrapping — the same envelope pattern Google's Tink library uses. Rotation re-wraps the small content key — multi-gigabyte payloads are never re-encrypted — and unwrap works across key rotation because the ciphertext itself names the CryptoKeyVersion.
• Bound wraps. Every wrap carries library-specific additional authenticated data (plus your bytes), and unwrap targets only the configured CryptoKey — a blob wrapped under a different key or AAD fails closed with PqDecryptionException, indistinguishable from tampering.
• CRC32C end to end. The integrity checksums Cloud KMS offers are populated on every request and verified on every response (the .NET SDK does not do this for you); a mismatch fails the operation instead of trusting a corrupted round-trip.
• Operational errors stay operational. Missing keys, permission denial, throttling, and network failures surface as the gRPC/SDK's own exceptions, not as decryption failures.
• IAM permission needed: cloudkms.cryptoKeyVersions.useToEncrypt to encrypt, cloudkms.cryptoKeyVersions.useToDecrypt to decrypt (both in roles/cloudkms.cryptoKeyEncrypterDecrypter).

Versioning

Kept in lockstep with PostQuantum.FileEncryption. No change to the .pqfe v2 container format, which remains FROZEN for the 1.x line.

To God be the glory — 1 Corinthians 10:31.