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Server-Side Encryption of Objects

MinIO Server-Side Encryption (SSE) protects objects as part of write operations, allowing clients to take advantage of server processing power to secure objects at the storage layer (encryption-at-rest). SSE also provides key functionality to regulatory and compliance requirements around secure locking and erasure.

MinIO SSE uses the MinIO Key Encryption Service (KES) and an external Key Management Service (KMS) for performing secured cryptographic operations at scale. MinIO also supports client-managed key management, where the application takes full responsibility for creating and managing encryption keys for use with MinIO SSE.

MinIO SSE is feature and API compatible with AWS Server-Side Encryption and supports the following encryption strategies:

MinIO supports enabling automatic SSE-KMS encryption of all objects written to a bucket using a specific External Key (EK) stored on the external KMS. Clients can override the bucket-default EK by specifying an explicit key as part of the write operation.

For buckets without automatic SSE-KMS encryption, clients can specify an EK as part of the write operation instead.

SSE-KMS provides more granular and customizable encryption compared to SSE-S3 and SSE-C and is recommended over the other supported encryption methods.

For a tutorial on enabling SSE-KMS in a local (non-production) MinIO Deployment, see Quickstart. For production MinIO deployments, use one of the following guides:

MinIO supports enabling automatic SSE-S3 encryption of all objects written to a bucket using an EK stored on the external KMS. MinIO SSE-S3 supports one EK for the entire deployment.

For buckets without automatic SSE-S3 encryption, clients can request SSE encryption as part of the write operation instead.

For a tutorial on enabling SSE-s3 in a local (non-production) MinIO Deployment, see Quickstart. For production MinIO deployments, use one of the following guides:

Clients specify an EK as part of the write operation for an object. MinIO uses the specified EK to perform SSE-S3.

SSE-C does not support bucket-default encryption settings and requires clients perform all key management operations.

MinIO SSE requires enabling Network Encryption (TLS).

Secure Erasure and Locking

MinIO requires access to the Encryption Key (EK) and external Key Management System (KMS) used as part of SSE operations to decrypt an object. You can use this dependency to securely erase and lock objects from access by disabling access to the EK or KMS used for encryption.

General strategies include, but are not limited to:

  • Seal the KMS such that it cannot be accessed by MinIO server anymore. This locks all SSE-KMS or SSE-S3 encrypted objects protected by any EK stored on the KMS. The encrypted objects remain unreadable as long as the KMS remains sealed.

  • Seal/Unmount an EK. This locks all SSE-KMS or SSE-S3 encrypted objects protected by that EK. The encrypted objects remain unreadable as long as the CMK(s) remains sealed.

  • Delete an EK. This renders all SSE-KMS or SSE-S3 encrypted objects protected by that EK as permanently unreadable. The combination of deleting an EK and deleting the data may fulfill regulatory requirements around secure deletion of data.

    Deleting an EK is typically irreversible. Exercise extreme caution before intentionally deleting a master key.

For more information, see:

Encryption Internals

Note

The following section describes MinIO internal logic and functionality. This information is purely educational and is not necessary for configuring or implementing any MinIO feature.

Content Encryption

The MinIO server uses an authenticated encryption scheme (AEAD) to en/decrypt and authenticate the object content. The AEAD is combined with some state to build a Secure Channel. A Secure Channel is a cryptographic construction that ensures confidentiality and integrity of the processed data. In particular, the Secure Channel splits the plaintext content into fixed size chunks and en/decrypts each chunk separately using an unique key-nonce combination.

The following text diagram illustrates Secure Channel Construction of an encrypted object:

The Secure Channel splits the object content into chunks of a fixed size of 65536 bytes. The last chunk may be smaller to avoid adding additional overhead and is treated specially to prevent truncation attacks. The nonce value is 96 bits long and generated randomly per object / multi-part part. The Secure Channel supports plaintexts up to 65536 * 2^32 = 256 TiB.

For S3 multi-part operations, each object part is en/decrypted with the Secure Channel Construction scheme shown above. For each part, MinIO generates a secret key derived from the Object Encryption Key (OEK) and the part number using a pseudo-random function (PRF), such that key = PRF(OEK, part_id).

Cryptographic Primitives

The MinIO server uses the following cryptographic primitive implementations:

Primitives

Pseudo-Random Functions (PRF)

HMAC-SHA-256

AEAD

ChaCha20Poly-1305 by default.

AES-256-GCM for x86-64 CPUs with the AES-NI extension.