Breaking Kerberos' RC4 Cipher and Spoofing Windows PACs

While the Active Directory implementation of Kerberos prefers to use cryptography based on AES, the deprecated Kerberos encryption type is still supported by default and widely used in practice. The property that RC4 derives its cryptographic keys from a user's NTLM hash is frequently exploited to authenticate without the original password (overpass-the-hash) or to efficiently brute-force service account passwords offline (Kerberoasting).No attacks were yet known that take advantage of the well-known weaknesses in Kerberos' RC4 implementation. Therefore I decided to …

account active directory aes attacks brute-force cipher cryptography default directory encryption exploited flaw hash kerberos keys ntlm password passwords practice rc4 service spoofing well-known windows