Software Verification and Analysis Using Z3

We provide a technical introduction on how to leverage the Z3 Theorem Prover to reason about the correctness of cryptographic software, protocols and otherwise, and to identify potential security vulnerabilities. We cover two distinct use cases: modeling and analysis of an algorithm documented in an old version of the QUIC Transport protocol IETF draft; modeling of specific finite field arithmetic operations for elliptic curve cryptography, with integers represented using a uniform saturated limb schedule, to prove equivalence with arbitrary-precision arithmetic, and for test cases generation.

Real World Cryptography Conference 2021: A Virtual Experience

Earlier this month, our Cryptography Services team got together and attended (virtually) the IACR's annual Real World Cryptography (RWC) conference. RWC is a fantastic venue for the latest results in real world cryptography from industry and academia. Holding this conference virtually inevitably introduced some changes: to accommodate as many time zones as possible, the daily … Continue reading Real World Cryptography Conference 2021: A Virtual Experience

Public Report – BLST Cryptographic Implementation Review

In October 2020, Supranational, Protocol Labs and the Ethereum Foundation engaged NCC Group’s Cryptography Services team to conduct a cryptographic implementation review of the BLST library. This library implements support for the draft IETF specifications on Hashing to Elliptic Curves and BLS Signatures. The latter specification uses advanced cryptographic-pairing operations to feature aggregation properties for … Continue reading Public Report – BLST Cryptographic Implementation Review

Double-odd Elliptic Curves

This post is about some new (or sort of new) elliptic curves for use in cryptographic protocols. They were made public in mid-December 2020, on a dedicated Web site: https://doubleodd.group/There is also a complete whitepaper, full of mathematical demonstrations, and several implementations. Oh noes, more curves! Will this never end? It is true that there … Continue reading Double-odd Elliptic Curves

Public Report – Filecoin Bellman and BLS Signatures Cryptographic Review

In May 2020, Protocol Labs engaged NCC Group's Cryptography Services team to conduct a cryptography review of multiple Filecoin code repositories. Filecoin is a decentralized storage and content distribution network developed by Protocol Labs. These repositories implement finite field and group arithmetic, cryptographic pairings, SHA2 via intrinsics, BLS signatures and zk-SNARK operations. Taken together, these … Continue reading Public Report – Filecoin Bellman and BLS Signatures Cryptographic Review

Faster Modular Inversion and Legendre Symbol, and an X25519 Speed Record

Elliptic curves are commonly used to implement asymmetric cryptographic operations such as key exchange and signatures. These operations are used in many places, in particular to initiate secure network connections within protocols such as TLS and Noise. However, they are relatively expensive in terms of computing resources, especially for low-end embedded systems, which run on … Continue reading Faster Modular Inversion and Legendre Symbol, and an X25519 Speed Record

Public Report – Electric Coin Company NU4 Cryptographic Specification and Implementation Review

In June 2020, the Electric Coin Company engaged NCC Group to conduct a security review of the six Zcash Improvement Proposals (ZIPs) that constitute the core of the upcoming Canopy (https://z.cash/upgrade/canopy/) upgrade (also called "NU4") to the Zcash network. This upgrade coincides with the first Zcash halving and will initiate a new development fund for … Continue reading Public Report – Electric Coin Company NU4 Cryptographic Specification and Implementation Review

Technical Advisory – wolfSSL TLS 1.3 Client Man-in-the-Middle Attack (CVE-2020-24613)

wolfSSL is a C-language-based SSL/TLS library targeted at IoT, embedded, and RTOS environments. wolfSSL incorrectly implements the TLS 1.3 client state machine. This allows attackers in a privileged network position to completely impersonate any TLS 1.3 servers and read or modify potentially sensitive information between clients using the wolfSSL library and these TLS servers.

Pairing over BLS12-381, Part 3: Pairing!

This is the last of three code-centric blog posts on pairing based cryptography. Support for these operations in an Ethereum precompiled contract has been proposed [1], and support for a related pairing configuration in precompiled contracts is already in operation [2, 3]. The first post [4] covered modular arithmetic, finite fields, the embedding degree, and … Continue reading Pairing over BLS12-381, Part 3: Pairing!

Public Report – Qredo Apache Milagro MPC Cryptographic Assessment

During the spring of 2020, Qredo engaged NCC Group Cryptography Services to conduct a security assessment of the Apache Milagro MPC library. This library implements the primitives necessary to instantiate the multi-party ECDSA signature scheme provided in Gennaro and Goldfeder’s Fast Multiparty Threshold ECDSA with Fast Trustless Setup. This assessment occurred over the course of … Continue reading Public Report – Qredo Apache Milagro MPC Cryptographic Assessment