Cryptanalysis of QTL Block Cipher
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- 关键词：Cryptography ; Lightweight block cipher ; Related ; key attacks ; Self ; similarity cryptanalysis ; QTL cipher
- 刊名：Lecture Notes in Computer Science
- 出版年：2017
- 出版时间：2017
- 年：2017
- 卷：10098
- 期：1
- 页码：60-68
- 丛书名：Lightweight Cryptography for Security and Privacy
- ISBN：978-3-319-55714-4
- 卷排序：10098
文摘
QTL is an ultra-lightweight block cipher designed for extremely constrained devices. The cipher has two versions, QLT-64 and QTL-128 supporting key lengths of 64 and 128 bits, respectively. In this paper, we present the first third party cryptanalysis of QTL. We first introduce related key distinguishers for full versions of the cipher. We propose attacks on full QTL in single key model by using the related key distinguishers. With these attacks we are able to reduce the security of QTL-64 and QTL-128 by 16 bits. We also enumerate \(2^{48}\) weak keys and propose a practical key recovery attack on full QTL-64 for these keys. This attack requires \(2^{16}\) data and recovers the key in a time complexity of \(2^{32}\) encryptions. We also give some observations disprove designers’ claims about number of active S-boxes and actual value of differential branch number.