What is Key Rotation?

Key Rotation: Definition

Key rotation, also known as cryptographic key rotation, is a controlled process of replacing an existing key with a new one on a defined schedule or after a specific event occurs. In practice, the goal is to limit how long a single encryption key remains active and to reduce the impact of possible exposure, theft, or misconfiguration.

In the context of photo and video anonymization, key rotation primarily applies to protecting source materials, post-anonymization files, working copies, metadata, exports, and system configuration. It is not the mechanism that actually blurs faces or license plates, but it is a critical part of securing the entire processing workflow. If an organization stores images or recordings before anonymization, the keys used to encrypt that data should be rotated regularly in line with its security policy.

From the perspective of standards and best practices, key rotation is closely tied to cryptographic key lifecycle management. NIST defines this area in NIST SP 800-57 Part 1 Rev. 5 from 2020, which describes key generation, distribution, use, archival, revocation, and destruction. In turn, NIST SP 800-38D sets requirements for AES-GCM, including risks associated with improper use of parameters such as a nonce or IV. In enterprise environments, key rotation is also part of compliance with ISO/IEC 27001:2022 and ISO/IEC 27002:2022, which require cryptographic controls and formal key management rules.

The Role of Key Rotation in Photo and Video Anonymization

In systems designed for visual data anonymization, cryptographic keys are not responsible for detecting faces or license plates. Those tasks are handled by detection models, usually based on deep learning, which identify objects within an image or video frame. Key rotation, by contrast, protects the data processed by that system.

In practice, this includes several layers of protection:

• encryption of input files - materials before blurring that contain personal data,
• encryption of output files - if the output may still contain confidential information or requires operational protection,
• protection of databases and metadata - for example, job IDs, processing statuses, and file paths,
• protection of backups - because backups often retain data longer than production systems,
• protection of system secrets - such as API keys, service passwords, and keys for object storage.

In an on-premises environment, key rotation is especially important because the organization itself is responsible for the infrastructure, storage of materials, and configuration of encryption modules. If the system processes CCTV footage, evidentiary materials, incident documentation, or photos from field audits, reducing the exposure of a single key directly lowers the risk of a confidentiality breach.

How Key Rotation Works in Practice

Key rotation can be implemented in several ways. The differences depend on whether the data encryption key, the master key protecting other keys, or both types are replaced at the same time. In systems that process photos and video, a layered approach is often used.

The most common elements are:

• DEK - Data Encryption Key - a key used to encrypt a specific file, a group of files, or a data volume,
• KEK - Key Encryption Key - a key used to encrypt or wrap DEKs,
• master key - a top-level key typically stored in an HSM, KMS, or another isolated component.

In an envelope encryption model, rotation may involve only the KEK, without re-encrypting all source files. This reduces operational cost. However, if the security policy requires a full change of cryptographic material, re-encryption is performed, meaning the data itself is encrypted again with a new DEK. This process is more resource-intensive and requires integrity checks.

A simplified representation is as follows:

Encrypted data = Encrypt(DEK, file)

Protected DEK = Wrap(KEK, DEK)

After KEK rotation, the system decrypts the previously wrapped DEK and protects it again with the new KEK. After DEK rotation, the data itself must be re-encrypted.

Key Rotation Parameters and Metrics

Assessing key rotation should not stop at confirming that a key has been changed. In environments that process images and recordings, technical, timing, and operational parameters matter.

There is no single universal key rotation interval suitable for every system. NIST indicates that the length of a cryptoperiod depends on the algorithm, key length, threat environment, number of operations, and the value of the protected information. This means that a rotation policy for a short-term photo archive may differ from one designed for a highly sensitive, long-term video repository.

Technologies and Standards Related to Key Rotation

Key rotation should be based on proven algorithms and sound key management procedures. In practice, symmetric encryption is commonly used to protect video and image files, while key management itself may be handled locally or by a dedicated module.

The most common technical references include:

• AES - the FIPS 197 standard, editorially updated by NIST in 2023,
• AES-GCM - an authenticated encryption mode described in NIST SP 800-38D from 2007,
• NIST SP 800-57 Part 1 Rev. 5 - cryptographic key management, 2020,
• ISO/IEC 27001:2022 and ISO/IEC 27002:2022 - organizational security requirements and controls,
• FIPS 140-3 - requirements for cryptographic modules; the standard was published in 2019 and replaced FIPS 140-2 in CMVP validation processes.

If the environment uses an HSM or a KMS, key rotation can be partly automated and fully auditable. In an on-premises system, it is important to separate administrative roles, key storage, and access to the video materials themselves. Encrypting data without a key rotation policy and without tracking key versions does not meet the goal of operational security.

Challenges and Limitations of Key Rotation

Key rotation improves security, but if poorly designed, it can increase the risk of losing access to data. This is particularly relevant for video archives, which are large, retained for long periods, and often subject to evidentiary or compliance requirements.

The most common issues are:

• no mapping of which file was encrypted with which key and in which version,
• incomplete rotation covering only the production system, without backups and test environments,
• re-encryption performed without validating file integrity after the operation,
• old keys left in active use despite formal rotation,
• no emergency procedure for materials important for audits or investigations.

In image processing environments, it is also important to distinguish between data protection and the operation of AI models. A model that detects faces or license plates does not replace cryptographic controls. If input material is stored without proper key protection, blurring performed later does not eliminate the earlier risk of a confidentiality breach.

Importance for GDPR Compliance and Data Security

The GDPR does not impose a specific algorithm or a fixed key rotation schedule, but it does require appropriate technical and organizational measures. The key provisions here are Article 5(1)(f) and Article 32 of the GDPR, which refer to integrity, confidentiality, and security of processing. In practice, key rotation is one of the mechanisms used to achieve these objectives, especially when an organization stores materials before anonymization.

For a Data Protection Officer, it is important that the key rotation policy is documented and tied to a risk assessment. At a minimum, it should specify:

• which data classes are covered by encryption,
• which key types are used,
• when scheduled and incident-driven rotation takes place,
• who approves and performs the operation,
• how the key version and operation result are documented.

In systems such as Gallio PRO, key rotation relates to the security of the processing environment and file storage. It does not change the fact that automatic detection applies to faces and license plates, while other image elements may require manual work in the editor. From a privacy protection perspective, these two areas are complementary: anonymization reduces identifiability in the material, while key rotation reduces the risk of unauthorized access to data before and after processing.