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Server-Side Encryption with Client-Managed Keys (SSE-C)

minio

Table of Contents

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.

The procedure on this page configures and enables Server-Side Encryption with Client-Managed Keys (SSE-C). MinIO SSE-C supports client-driven encryption of objects before writing the object to disk. Clients must specify the correct key to decrypt objects for read operations.

MinIO SSE-C is functionally compatible with Amazon Server-Side Encryption with Customer-Provided Keys <ServerSideEncryptionCustomerKeys.html>.

Secure Erasure and Locking

SSE-C protects objects using an EK (External Key) specified by the client as part of the write operation. Assuming the client-side key management supports disabling or deleting these keys:

  • Disabling the EK (External Key) temporarily locks any objects encrypted using that

    EK (External Key) by rendering them unreadable. You can later enable the EK (External Key) to resume normal read operations on those objects.

  • Deleting the EK (External Key) renders all objects encrypted by that EK (External Key)

    permanently unreadable. If the client-side KMS does not support backups of the EK (External Key), this process is irreversible.

The scope of a single EK (External Key) depends on the number of write operations which specified that EK (External Key) when requesting SSE-C encryption.

Considerations

SSE-C is Incompatible with Bucket Replication

SSE-C encrypted objects are not compatible with MinIO bucket replication <minio-bucket-replication>. Use SSE-KMS <minio-encryption-sse-kms> or SSE-S3 <minio-encryption-sse-s3> to ensure encrypted objects are compatible with bucket replication.

SSE-C Overrides SSE-S3 and SSE-KMS

Encrypting an object using SSE-C prevents MinIO from applying SSE-KMS <minio-encryption-sse-kms> or SSE-S3 <minio-encryption-sse-s3> encryption to that object.

Quickstart

MinIO SSE-C requires the client to perform all key creation and storage operations.

This procedure uses mc for performing operations on the source MinIO deployment. Install mc on a machine with network access to the source deployment. See the mc Installation Quickstart <mc-install> for instructions on downloading and installing mc.

The SSE-C key must be a 256-bit base64-encoded string. The client application is responsible for generation and storage of the encryption key. MinIO does not store SSE-C encryption keys and cannot decrypt SSE-C encrypted objects without the client-managed key.

1) Generate the Encryption Key

Generate the 256-bit base64-encoded string for use as the encryption key.

The following example generates a string that meets the encryption key requirements. The resulting string is appropriate for non-production environments:

cat /dev/urandom | head -c 32 | base64 -

Defer to your organizations requirements for generating cryptographically secure encryption keys.

Copy the encryption key for use in the next step.

2) Encrypt an Object using SSE-C

MinIO supports the following AWS S3 headers for specifying SSE-C encryption:

  • X-Amz-Server-Side-Encryption-Customer-Algorithm set to AES256.
  • X-Amz-Server-Side-Encryption-Customer-Key set to the encryption key value.
  • X-Amz-Server-Side-Encryption-Customer-Key-MD5 to the 128-bit MD5 digest of the encryption key.

The MinIO mc commandline tool S3-compatible SDKs include specific syntax for setting headers. Certain mc commands like mc cp include specific arguments for enabling SSE-S3 encryption:

mc cp ~/data/mydata.json ALIAS/BUCKET/mydata.json \
   --encrypt-key "ALIAS/BUCKET/=c2VjcmV0ZW5jcnlwdGlvbmtleWNoYW5nZW1lMTIzNAo="
  • Replace ALIAS <mc encrypt set ALIAS> with the alias <mc alias> of the MinIO deployment on which you want to write the SSE-C encrypted object.
  • Replace BUCKET <mc encrypt set ALIAS> with the full path to the bucket or bucket prefix to which you want to write the SSE-C encrypted object.

3) Copy an SSE-C Encrypted Object

MinIO supports the following AWS S3 headers for copying an SSE-C encrypted object to another S3-compatible service:

  • X-Amz-Copy-Source-Server-Side-Encryption-Algorithm set to AES256
  • X-Amz-Copy-Source-Server-Side-Encryption-Key set to the encryption key value. The copy operation will fail if the specified key does not match the key used to SSE-C encrypt the object.
  • X-Amz-Copy-Source-Server-Side-Encryption-Key-MD5 set to the 128-bit MD5 digest of the encryption key.

The MinIO mc commandline tool S3-compatible SDKs include specific syntax for setting headers. Certain mc commands like mc cp include specific arguments for enabling SSE-S3 encryption:

mc cp SOURCE/BUCKET/mydata.json TARGET/BUCKET/mydata.json  \
   --encrypt-key "SOURCE/BUCKET/=c2VjcmV0ZW5jcnlwdGlvbmtleWNoYW5nZW1lMTIzNAo=" \
   --encrypt-key "TARGET/BUCKET/=c2VjcmV0ZW5jcnlwdGlvbmtleWNoYW5nZW1lMTIzNAo="
  • Replace SOURCE/BUCKET <mc encrypt set ALIAS> with the alias <mc alias> of the MinIO deployment from which you are reading the encrypted object and the full path to the bucket or bucket prefix from which you want to read the SSE-C encrypted object.
  • Replace TARGET/BUCKET <mc encrypt set ALIAS> with the alias <mc alias> of the MinIO deployment from which you are writing the encrypted object and the full path to the bucket or bucket prefix to which you want to write the SSE-C encrypted object.