NCSC Guidance on “Advanced Cryptography”

The UK’s National Cyber Security Centre just released its white paper on “Advanced Cryptography,” which it defines as “cryptographic techniques for processing encrypted data, providing enhanced functionality over and above that provided by traditional cryptography.” It includes things like homomorphic encryption, attribute-based encryption, zero-knowledge proofs, and secure multiparty computation.

It’s full of good advice. I especially appreciate this warning:

When deciding whether to use Advanced Cryptography, start with a clear articulation of the problem, and use that to guide the development of an appropriate solution. That is, you should not start with an Advanced Cryptography technique, and then attempt to fit the functionality it provides to the problem. …

May 2, 2025
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AIs as Trusted Third Parties

This is a truly fascinating paper: “Trusted Machine Learning Models Unlock Private Inference for Problems Currently Infeasible with Cryptography.” The basic idea is that AIs can act as trusted third parties:

Abstract: We often interact with untrusted parties. Prioritization of privacy can limit the effectiveness of these interactions, as achieving certain goals necessitates sharing private data. Traditionally, addressing this challenge has involved either seeking trusted intermediaries or constructing cryptographic protocols that restrict how much data is revealed, such as multi-party computations or zero-knowledge proofs. While significant advances have been made in scaling cryptographic approaches, they remain limited in terms of the size and complexity of applications they can be used for. In this paper, we argue that capable machine learning models can fulfill the role of a trusted third party, thus enabling secure computations for applications that were previously infeasible. In particular, we describe Trusted Capable Model Environments (TCMEs) as an alternative approach for scaling secure computation, where capable machine learning model(s) interact under input/output constraints, with explicit information flow control and explicit statelessness. This approach aims to achieve a balance between privacy and computational efficiency, enabling private inference where classical cryptographic solutions are currently infeasible. We describe a number of use cases that are enabled by TCME, and show that even some simple classic cryptographic problems can already be solved with TCME. Finally, we outline current limitations and discuss the path forward in implementing them…

March 28, 2025
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Implementing Cryptography in AI Systems

Interesting research: “How to Securely Implement Cryptography in Deep Neural Networks.”

Abstract: The wide adoption of deep neural networks (DNNs) raises the question of how can we equip them with a desired cryptographic functionality (e.g, to decrypt an encrypted input, to verify that this input is authorized, or to hide a secure watermark in the output). The problem is that cryptographic primitives are typically designed to run on digital computers that use Boolean gates to map sequences of bits to sequences of bits, whereas DNNs are a special type of analog computer that uses linear mappings and ReLUs to map vectors of real numbers to vectors of real numbers. This discrepancy between the discrete and continuous computational models raises the question of what is the best way to implement standard cryptographic primitives as DNNs, and whether DNN implementations of secure cryptosystems remain secure in the new setting, in which an attacker can ask the DNN to process a message whose “bits” are arbitrary real numbers…

February 21, 2025
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List of Old NSA Training Videos

The NSA’s “National Cryptographic School Television Catalogue” from 1991 lists about 600 COMSEC and SIGINT training videos.
There are a bunch explaining the operations of various cryptographic equipment, and a few code words I have ne…

September 3, 2024
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“YOLO” is not a valid hash construction

By Opal Wright Among the cryptographic missteps we see at Trail of Bits, “let’s build our own tool out of a hash function” is one of the most common. Clients have a problem along the lines of “we need to hash a bunch of different values together” or “we need a MAC” or “we need […]

August 21, 2024
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We wrote the code, and the code won

By Tjaden Hess Earlier this week, NIST officially announced three standards specifying FIPS-approved algorithms for post-quantum cryptography. The Stateless Hash-Based Digital Signature Algorithm (SLH-DSA) is one of these standardized algorithms. The Trail of Bits cryptography team has been anticipating this announcement, and we are excited to share an announcement of our own: we built an […]

August 15, 2024
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Cloud cryptography demystified: Google Cloud Platform

By Scott Arciszewski This post, the second in our series on cryptography in the cloud, provides an overview of the cloud cryptography services offered within Google Cloud Platform (GCP): when to use them, when not to use them, and important usage considerations. Stay tuned for future posts covering other cloud services. At Trail of Bits, […]

August 5, 2024
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