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Key rotation

Cryptographic keys play a pivotal role in safeguarding data, but they are not invincible to theft or compromise over time. These keys are often accessible to multiple components within your architecture. If one service is compromised, all data encrypted with its key becomes vulnerable.

This is why we can’t simply “set and forget” cryptographic keys. A proactive approach is necessary to limit potential damage in the event of a key compromise. Regular key rotation, which involves replacing cryptographic keys at predefined intervals or after specific incidents, is the solution.

Why rotate keys?

Here are a few reasons why key rotation should be part of your key management practices:

  1. Key rotation limits the amount of data encrypted with a single key, mitigating potential damage in case of a key compromise.
  2. Regularly rotating keys reinforces confidentiality, integrity, and availability by reducing the risk of unauthorized data access.
  3. Developers and DevOps sometimes copy and share encryption keys in unsafe ways (such as on Slack or via email) that preserve them in history, rendering the keys unsafe.
  4. Various laws and regulations, such as the GDPR, HIPAA, and PCI-DSS, emphasize the importance of cryptography and key rotation to ensure data confidentiality.

Key rotation vs. re-keying vs. re-encryption

Key rotation? Re-keying? Re-encryption? These terms often intertwine, causing confusion. Why should encryption keys be periodically changed, and how do these processes differ?

Encryption is a critical tool for protecting sensitive data. It depends on a secret key to secure each message. But what if that key is leaked? What measures can mitigate the risk? The answers lie in the following terms:

  • Key rotation. The practice of periodically introducing a new encryption key and retiring the old one. It’s a proactive measure to reduce the damage from a potential key leak, similar to a relay race where responsibilities are handed from one key to another.
  • Re-encryption. Involves decrypting previously encrypted data with the old key and encrypting it again with a new key.
  • Re-keying. Refers to changing an encryption key during ongoing communication sessions (e.g., TLS sessions). This applies to encrypting data in transit, while key rotation and re-encryption apply to data at rest.

Key rotation can be based on time or usage. By limiting the amount of data encrypted with a single key, rotation reduces the impact of a compromised key. In cases of suspected key leaks, immediate key rotation combined with re-encryption provides a reactive defense to protect data.

Key rotation is not just a best practice; it is also advocated or required by regulations such as the GDPR, HIPAA, and PCI-DSS.

If you want to know more about key rotation, including available strategies, challenges, and best practices, as well as examples of implementing key rotation for symmetric an asymmetric encryption, see The Importance of Key Rotation for Data Security.