Password Compromise Checking Service

Modern information security standards require information systems to check user passwords against a «blacklist» before installation, since typical password policies (minimum password length, minimum number of different character types) do not protect against the use of weak passwords such as «Pasword1» or «ILoveYou». This thesis is intended to implement and compare two different protocols for anonymous password verification against a compromised password database: a protocol using the k-anonymity[1] approach based on a hash function and a protocol using the Private Set Intersection[2] algorithm, which allows the server not to disclose information about the compromised password database. This paper contains 51 pages, 4 chapters, 14 figures, 3 tables, 48 sources. Keywords: Cybersecurity, Password authentication, Password policies, Compromised password databases, K-anonymity, Private Set Intersection (PSI) algorithm, Commutative encryption, Credential stuffing.