Re: [Cfrg] Analysis of ipcrypt?
Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com> Thu, 22 February 2018 06:55 UTC
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From: Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
Date: Thu, 22 Feb 2018 06:55:17 +0000
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To: Paul Hoffman <paul.hoffman@icann.org>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>, "cfrg@irtf.org" <cfrg@irtf.org>
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Subject: Re: [Cfrg] Analysis of ipcrypt?
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Hi! I designed ipcrypt as a low-security toy cipher to encrypt IPv4 addresses for some log analysis application. It may be good enough for this purpose, however it has very low security: * because of 32-bit blocks, a chosen-plaintext codebook attack will work in time 2^32 (or much less for specific IP ranges) * known-plaintext codebook attacks will work similarly but in O(n log n), or 2^37 (coupon collector problem) * there is a generic ~2^16 distinguisher that works by looking for a collision in a sequence of blocks * worse, Jason just found a high-probability differential that seems detectable with fewer than 2^24 chosen-plaintext pair, and which may speed up key recovery On Thu, 22 Feb 2018 at 03:03, Paul Hoffman <paul.hoffman@icann.org> wrote: > Greetings. ipcrypt is a format-preserving cipher for IPv4 addresses. It > has a 32-bit blocksize for input and output, and 128-bit blocksize for the > key. It was developed by Jean-Philippe Aumasson and is described at: > https://github.com/veorq/ipcrypt > There doesn't appear to be any formal paper describing the algorithm, but > the Python and Go code is trivial to follow. > > This algorithm is now being considered by a few different projects that > want to obfuscate IPv4 addresses. Has anyone analyzed the algorithm? I > could not find analyses, but certainly could have missed them. > > For a project I'm on, ipcrypt is attractive if an attacker cannot derive > the 128-bit random key without a lot (maybe 2^80ish) effort. For cases in > common use, assume that the attacker has 2^24 known plaintext/ciphertext > pairs under a single 128-bit random key. For additional ciphertexts, how > much effort must the attacker expend to get the key in order to decrypt > additional unknown ciphertexts? > > (Note that there are other options for this use case, which have different > positive and negative features. What we'd like to know is how good is > ipcrypt if we chose it.) > > --Paul Hoffman_______________________________________________ > Cfrg mailing list > Cfrg@irtf.org > https://www.irtf.org/mailman/listinfo/cfrg >
- [Cfrg] Analysis of ipcrypt? Paul Hoffman
- Re: [Cfrg] Analysis of ipcrypt? Jean-Philippe Aumasson
- Re: [Cfrg] Analysis of ipcrypt? Jason A. Donenfeld
- Re: [Cfrg] Analysis of ipcrypt? Greg Rose
- Re: [Cfrg] Analysis of ipcrypt? Russ Housley
- Re: [Cfrg] Analysis of ipcrypt? Daniel Kahn Gillmor
- Re: [Cfrg] Analysis of ipcrypt? Daniel Kahn Gillmor
- Re: [Cfrg] Analysis of ipcrypt? Greg Rose
- Re: [Cfrg] [Ext] Re: Analysis of ipcrypt? Paul Hoffman
- Re: [Cfrg] Analysis of ipcrypt? Martin Thomson
- Re: [Cfrg] [Ext] Re: Analysis of ipcrypt? Greg Rose
- Re: [Cfrg] [Ext] Re: Analysis of ipcrypt? Scott Fluhrer (sfluhrer)
- Re: [Cfrg] [Ext] Re: Analysis of ipcrypt? David McGrew (mcgrew)
- Re: [Cfrg] Analysis of ipcrypt? Russ Housley
- Re: [Cfrg] [Ext] Re: Analysis of ipcrypt? Jean-Philippe Aumasson
- Re: [Cfrg] [Ext] Re: Analysis of ipcrypt? Greg Rose
- Re: [Cfrg] [Ext] Re: Analysis of ipcrypt? Jean-Philippe Aumasson
- Re: [Cfrg] [Ext] Re: Analysis of ipcrypt? Paul Hoffman
- Re: [Cfrg] [Ext] Re: Analysis of ipcrypt? Jean-Philippe Aumasson
- Re: [Cfrg] [Ext] Re: Analysis of ipcrypt? Paul Hoffman
- Re: [Cfrg] [Ext] Re: Analysis of ipcrypt? Jean-Philippe Aumasson
- Re: [Cfrg] Analysis of ipcrypt? Tim Hollebeek