Through a combination of hardware failure and human error, the decryption key for a bank’s...

Under the GDPR (Article 4(12)), a personal data breach is defined as:

"A breach of security leading to the accidental or unlawful destruction, loss, alteration, unauthorized disclosure of, or access to, personal data transmitted, stored, or otherwise processed"​.

Why Answer Choice D is Correct

Loss of Encryption Key = Loss of Data Availability

The loss of the decryption key means that the bank can no longer access customer transaction data.

Availability is a fundamental aspect of data security (Article 32). Loss of availability constitutes a breach under GDPR​.

Loss of Confidentiality & Integrity

If the encryption key is lost, data cannot be decrypted, meaning it is effectively destroyed or altered.

This qualifies as a data breach under GDPR since data integrity and confidentiality are compromised​.

Why Other Answer Choices Are Incorrect:

A (No Breach Because No Hacking):

GDPR does not require hacking for a breach to occur. A loss of access alone can qualify​.

B (No Breach Because No Unauthorized Access):

Unauthorized disclosure is one type of breach, but GDPR also covers loss and destruction of personal data​.

C (Data Breach Due to Inaccessibility):

Partially correct but does not fully explain the GDPR criteria. GDPR defines breaches in terms of confidentiality, integrity, and availability—all of which are affected​.

Conclusion:

This incident is a data breach under GDPR, as it impacts data confidentiality, integrity, and availability.

The correct answer is D, because losing the decryption key compromises data integrity and availability, qualifying as a data breach under GDPR Article 4(12)​.