SHA-1

Hash Functions Part 1: Core Properties, Security Requirements and Practical Applications

The article provides a detailed introduction to hash functions, explaining how they map arbitrary-length input to fixed-length output while satisfying three fundamental security properties. It covers preimage resistance, second preimage resistance, and collision resistance, along with the avalanche effect that makes even minor input changes produce unrecognizable output. The text explains why a 256-bit digest is required to achieve 128-bit collision resistance, referencing the birthday paradox and its implications for MD5 and SHA-1. Practical guidance includes using OpenSSL for hashing, applying hashes in commitment schemes, enforcing subresource integrity on web pages, and securely storing passwords with Argon2 and bcrypt. The post emphasizes that hash functions alone do not guarantee integrity without proper transmission of the digest and announces a follow-up on SHA-2 and SHA-3 internals.

Web Certificate Trust Chains and State Access Risks Explained Amid Russian Banking Sanctions

The article explains the hierarchical structure of web certificates used for site authentication and traffic encryption, starting from highly protected root certificates stored in air-gapped facilities with Shamir's secret sharing for key protection. Intermediate certificates extend the chain of trust down to leaf certificates deployed on websites. Russian banks have turned to certificates issued under the MinTsifry root after Western and Chinese CAs refused service due to sanctions. The piece highlights that any nation-state with access to a root private key, whether FSB, NSA, or others, could theoretically issue fraudulent certificates for any domain. It notes the limitations of the X.509 standard, which lacks native support for multi-CA signatures, and suggests that separate browsing environments or PGP-style web-of-trust models could mitigate risks. The author concludes that security is already reduced by reliance on any state-controlled CA and that the choice is ultimately which intelligence agency one prefers to trust.