Paul Bottinelli

Dancing Offbit: The Story of a Single Character Typo that Broke a ChaCha-Based PRNG

Random number generators are the backbone of most cryptographic protocols, the crucial cornerstone upon which the security of all systems rely, yet they remain often overlooked. This blog post presents a real-world vulnerability discovered in the implementation of a Pseudo-Random Number Generator (PRNG) based on the ChaCha20 cipher. Discovery of…

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August 22, 2023

5 mins read

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Breaking Pedersen Hashes in Practice

The Pedersen hash function has gained popularity due to its efficiency in the arithmetic circuits used in zero-knowledge proof systems. Hash functions are a crucial primitive in cryptography, and zero-knowledge proof systems often make heavy use of them, for example when computing Merkle tree roots and paths. Instead of being…

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March 22, 2023

14 mins read

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An Illustrated Guide to Elliptic Curve Cryptography Validation

Elliptic Curve Cryptography (ECC) has become the de facto standard for protecting modern communications. ECC is widely used to perform asymmetric cryptography operations, such as to establish shared secrets or for digital signatures. However, insufficient validation of public keys and parameters is still a frequent cause of confusion, leading to…

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Technical Advisory – Arbitrary Signature Forgery in Stark Bank ECDSA Libraries (CVE-2021-43572, CVE-2021-43570, CVE-2021-43569, CVE-2021-43568, CVE-2021-43571)

Summary Stark Bank is a financial technology company that provides services to simplify and automate digital banking, by providing APIs to perform operations such as payments and transfers. In addition, Stark Bank maintains a number of cryptographic libraries to perform cryptographic signing and verification. These popular libraries are meant to…

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Security Considerations of zk-SNARK Parameter Multi-Party Computation

The secure generation of parameters for zk-SNARKs is a crucial step in the trustworthiness of the resulting proof system. By highlighting some potential pitfalls and important security considerations of these implementations, NCC Group hopes to provide helpful pointers to all implementers and avoid the introduction of vulnerabilities detrimental to the…

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June 24, 2020

13 mins read

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How cryptography is used to monitor the spread of COVID-19

On April 10, Apple and Google announced1, 2 that they were joining forces in an effort to help reduce the spread of COVID-19. Their solution leverages Bluetooth technology to trace interactions between individuals. This principle is known as contact tracing and public health agencies are heavily relying on it to…

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