Stateful Turing-Complete Policies

The Future of Access Control: Stateful Turing-Complete Policies

For over two decades, the internet has struggled with a seemingly simple yet insurmountable problem: securing user accounts. With hundreds of websites and dozens of passwords, users are constantly at risk of being hacked by increasingly sophisticated attackers. The patchwork of ad-hoc solutions, including password managers and centralized services, has failed to provide a comprehensive solution. It's time to rethink the way we approach access control.

The Limitations of Current Solutions

Traditional password-based access control systems are inherently flawed. Users are forced to remember multiple passwords, leading to a proliferation of weak or reused passwords. Even with password managers, the reliance on centralized services creates a single point of failure. Moreover, these solutions often fail to account for the complexities of modern applications, which require fine-grained access control and flexible policies.

The Power of Turing-Complete Code

To overcome these limitations, we need to introduce a new paradigm: Turing-complete code. By allowing access policies to be specified in code, executed in a deterministic virtual machine, we can create a more flexible and secure system. This approach enables users to define their own policies, using any cryptographic algorithm, including keys held on their computer, hardware devices, or any arbitrary combination of the above.

Operation-Dependent Code

For many applications, we need to authorize users to carry out specific operations, but not others. To accommodate this, we need to introduce operation-dependent code. A simple "Turing-complete-code as signature" setup might have the following form:

VM(code, server-provided nonce ++ signature) ?= 1

Where VM is a virtual machine that runs code, taking a server-provided nonce and a signature as input, and the verification check is to see whether or not the output is 1. A simple example of code that could be put in is an elliptic curve digital signature verifier.

Stateful Policies

However, even with operation-dependent code, we still need to account for more complex scenarios, such as withdrawal limits or key revocation. To get past this last hump, we need to introduce stateful policies, where operations can change the state of the policy. This is where blockchains come in, providing a convenient, credible, and standardized mechanism for users to download modules and support any blockchain or centralized solution.

Applications and Implications

The concept of stateful Turing-complete policies has far-reaching implications for various applications, including:

Account security: By allowing users to define their own policies, we can create a more secure and flexible system, where users can choose the level of security that suits their needs.
Domain name registry: With stateful Turing-complete policies, we can create a more dynamic and flexible system, where users can define their own auction algorithms and pricing policies.
Private stock trading: By allowing users to define their own policies, we can create a more secure and flexible system, where users can define their own restrictions and rules for stock trading.
Digital asset ownership: With stateful Turing-complete policies, we can create a more secure and flexible system, where users can define their own rules and restrictions for digital asset ownership.

Conclusion

The future of access control is stateful Turing-complete policies. By allowing users to define their own policies, using any cryptographic algorithm, we can create a more secure and flexible system. This approach has far-reaching implications for various applications, including account security, domain name registry, private stock trading, and digital asset ownership. As we move forward, it's essential to consider the power of Turing-complete code and its potential to revolutionize the way we approach access control.

Source: https://blog.ethereum.org/en/2015/11/09/stateful-turing-complete-policies