We present several practical key-recovery attacks against the OMA digest. The first and basic variant can achieve this with a mere $13$ queries to an OMA digest oracle and negligible time complexity. A more sophisticated version breaks the OMA digest with only $4$ queries and a time complexity of about $2^{25}$ simple operations. A different approach only requires one arbitrary valid plaintext-tag pair, and recovers the key in an average of $144$ \emph{message verification} queries, or one ciphertext-tag pair and $168$ \emph{ciphertext verification} queries.
Since the encryption key is derived from the key used by the OMA digest, our attacks break both confidentiality and authenticity of OSGP.
Category / Keywords: secret-key cryptography / cryptanalysis, smart grid, authenticated encryption Original Publication (with minor differences): IACR-FSE-2015 Date: received 27 Apr 2015, last revised 18 Jun 2015 Contact author: jovanovic at fim uni-passau de Available format(s): PDF | BibTeX Citation Version: 20150618:123954 (All versions of this report) Short URL: ia.cr/2015/428 Discussion forum: Show discussion | Start new discussion