报告题目: |
Improving Counter-cryptanalysis |
报告人: |
Dr. Marc Stevens |
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Centrum Wiskunde & Informatica, Netherlands
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报告时间: |
2013-09-02 09:00 |
报告地点: |
Conference Hall 322, Science Building, Tsinghua University |
主办单位: |
高等研究院 |
简介: |
Flame, a highly advanced malware for cyberwarfare discovered in May,
spread itself as a properly, but illegitimately, signed Microsoft Update security patch.
Flame achieved this by forging a signature from Microsoft using a so-called
chosen-prefix collision attack on the very weak cryptographic hash function MD5.
In this talk I will focus on counter-cryptanalysis, a new paradigm for strengthening
cryptographic primitives, and the first example thereof, namely an efficient anomaly
detection technique that detects whether a given signature was forged using
a cryptanalytic collision attack on the underlying hash function.
We used counter-cryptanalysis to expose Flame's yet unknown variant chosen-prefix
collision attack even though only one of the two colliding certificates was available.
Besides forensic analysis, counter-cryptanalysis can be effectively used
to detect whether digital signatures are possible forgeries created using a collision attack.
Finally, I will discuss ongoing work on improving the complexity of this new technique
and efforts to reduce the chance of false negatives,
i.e., existence of feasible yet-undetected collision attacks. |
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