What is Envelope encryption?

A scheme in which data are encrypted with a data encryption key (DEK), and the DEK is in turn encrypted (wrapped) with a separate key encryption key (KEK) and stored together with the data. The KEK stays inside a KMS or HSM and never leaves it, while large data can be encrypted locally. When the KEK is rotated, only the small DEKs need to be re-encrypted, not all of the data. It is widely used to encrypt cloud storage and databases.

Japanese name: エンベロープ暗号化

Envelope encryption appears in 1 practice question across 1 topic, including Applied Cryptography.

Field: Applied Cryptography

Try it: questions about Envelope encryption

Let DEK be a data encryption key and KEK a key encryption key. Which of the following correctly describes envelope encryption, as used in cloud storage and elsewhere?

AThe data are encrypted with a DEK, the DEK is encrypted with a KEK inside the key management service, and it is stored together with the data
BAll the data are sent to the key management service to be encrypted directly with a single key inside the key management service
CThe key used to encrypt the data is stored unencrypted in the same place as the ciphertext so that it is easy to retrieve

Show answer and explanation

Answer: A. The data are encrypted with a DEK, the DEK is encrypted with a KEK inside the key management service, and it is stored together with the data

In envelope encryption a DEK is created for each piece of data and the data are encrypted with symmetric-key encryption; the DEK is encrypted (wrapped) with a KEK inside a KMS or HSM and stored next to the encrypted data. Large data need not be sent to the key management service, and the KEK never leaves the device, so the keys that need the strictest protection can be kept to a few. When the KEK is rotated, only the small DEKs need to be re-encrypted, not all of the data. To read the data, the wrapped DEK is decrypted by the KMS and the data are decrypted locally.

Envelope encryption in the explanations

In envelope encryption a DEK is created for each piece of data and the data are encrypted with symmetric-key encryption; the DEK is encrypted (wrapped) with a KEK inside a KMS or HSM and stored next to the encrypted data.
Let DEK be a data encryption key and KEK a key encryption k…