Why Dark Crystal?

Dark Crystal is a protocol for distributed data persistence and threshold-based consensus. It is based on a secure implementation of Shamir’s Secret Sharing and has multiple possible applications in security-oriented tools.

Modern encryption techniques are strong, but rarely used by those who need them. A recurring reason for this is users’ fears of losing access to critical data: the ‘Global Encryption Trends Study 2018’, conducted by the Ponemon Institute, indicates that key management issues pose a major barrier to the adoption of encryption tools.

Mechanisms such as privately owned offline storage in a secure location, virtual private servers, a trustworthy and reliable cloud service, or the data storage infrastructure provided by certain NGOs, have their own intrinsic limitations. These methods require that users be conceptually comfortable with digital security issues and familiar with key management practices, such that they can back-up their keys (or data) independently of the related application.

Moreover, while traditional forms of ‘secure backup’ make sense for sensitive media such as incriminating photos, they are less suitable for personal cryptographic keys. In the case of signing keys for creating verifiable evidence, it would undermine the strength of this evidence if another party took complete custody of the key. In the case of encryption keys for personal messages, insecure or unencrypted backups can create a weak point in security. There are also security risks involved with transmitting cryptographic keys over the internet.

Given the vulnerability of centralised systems, we believe that offering users at least the option of distributed secure backups can at the very least provide a complementary alternative option for developers and users of encrypted tools.

Finally, as peer-to-peer protocols advance in response to widespread security concerns with centralised client-server architectures, key (and/or data) backup becomes an even more serious issue. Developing distributed backup and remote wipe features for peer-to-peer applications, to match features already available in client-server architectures, gives both developers and users a greater and more robust set of tools to choose from to address their particular digital security needs.

In general, Shamir’s scheme is considered information-theoretically secure. That is, individual shares contain absolutely no semantic information about the secret, and it can be said to be ‘post quantum’ cryptography. As an interesting anecdote, the root key for ICANN DNS security, effectively the key which secures the naming system of the internet, is held by seven parties, based in Britain, the U.S., Burkina Faso, Trinidad and Tobago, Canada, China, and the Czech Republic. Cryptographer Bruce Schneier has alleged that they are holders of Shamir’s secret shares, which indicates that the scheme is taken quite seriously.