We are happy to announce that our timed release encryption scheme "tlock (opens new window)" and its implementations, which we introduced in our previous blog post (opens new window), have recently undergone a comprehensive security assessment by Kudelski Security (opens new window). This was a crucial step in ensuring the robustness and reliability of our encryption system in order to guarantee that timelocked content remains encrypted until the time has come for it to be decrypted and never before.

Overview

Kudelski Security (opens new window), a renowned provider of cybersecurity solutions, was engaged to review the implementation of our timelock encryption scheme and timelock responsible disclosure demo. The work covered:

• tlock, our Go implementation (opens new window) as both a library and a command line tool (tle) for timelock encryption.
• tlock-js, our interoperable TypeScript implementation (opens new window) of timelock encryption.
• timevault, our web demo for timelock encryption, which is available at https://timevault.drand.love/ (opens new window).
• Their critical security dependencies.

The audit primarily focused on code security, protocol security and ensuring our implementations matched our tlock paper (opens new window).

Audit Findings

During the audit, Kudelski Security identified:

• 1 High severity issue
• 5 Medium severity issues
• 3 Low severity issues

It is worth highlighting that none of the identified issues would have put existing encrypted data at risk. We are pleased to report that all identified issues have been addressed and corrected. The detailed audit report is available on IPFS with CID QmWQvTdiD3fSwJgasPLppHZKP6SMvsuTUnb1vRP2xM7y4m (opens new window).

Security Considerations

The security of our timelock encryption system relies on four main aspects:

1. The security of the Identity Encryption Scheme (opens new window) from 2001 that we used, and our implementation of it.
2. The security of the underlying threshold BLS scheme (opens new window) from 2003 that we used, and our implementation of it.
3. The security of age's underlying primitives, and that of the age implementation used to encrypt the actual data. (See https://age-encryption.org/ (opens new window) for details about age.)
4. The security of the threshold network providing you with its BLS signatures at a given frequency.

Please note that neither the BLS, nor the IBE scheme are "quantum resistant". However, a quantum computer that is able to break them seems unlikely to be built within the next 5-10 years and therefore we currently consider that you can expect a "long term security" horizon of at least 5 years by relying on our design for timed release encryption.

Conclusion

We are grateful to the Kudelski Security Research team for their thorough and professional audit. Their expertise has been critical in helping us improve the security of drand's timelock encryption functionality. We also want to thank the Kudelski team for the smooth collaboration and availability throughout the assessment.

However, it's important to note that no security assessment can guarantee 100% security. While we've taken extensive measures to ensure the security of our timelock encryption system, we encourage users to understand the security considerations and make informed decisions, especially when encrypting data for a long time period.

Our code being entirely open-source, further scrutiny and reviews are always welcome. Don't hesitate to join our Slack workspace (opens new window) to discuss our Timelock design, possible use-cases, or to show us what you've done with it!

We look forward to continuing to enhance the security and reliability of our systems, and we remain committed to transparency and collaboration in all our endeavours.