Re: Decimal encryption

2008-08-28 Thread Hal Finney
I wrote: Looking a little more closely, I found this paper by Patarin from Crypto 2005 which describes security bounds for higher round Feistel constructions: http://www.springerlink.com/content/gtcabev3ucv8apdu/ I was wrong, this was from Crypto 03. And as Eric Rescorla has already pointed

Re: Decimal encryption

2008-08-28 Thread Hovav Shacham
- Jonathan Katz [EMAIL PROTECTED] wrote: But he probably wants an encryption scheme, not a cipher. Jon, I'm not sure I understand what you mean. If I am reading his message correctly, the original poster seems to be asking for a format-preserving encryption over a domain with 10^40

Re: Decimal encryption

2008-08-28 Thread Peter Gutmann
Eric Rescorla [EMAIL PROTECTED] writes: There are a set of techniques that allow you to encrypt elements of arbitrary sets back onto that set. ... and most of them seem to be excessively complicated for what they end up achieving. Just for reference the mechanism from the sci.crypt thread of

Re: Decimal encryption

2008-08-28 Thread Eric Rescorla
At Thu, 28 Aug 2008 17:32:10 +1200, Peter Gutmann wrote: Eric Rescorla [EMAIL PROTECTED] writes: There are a set of techniques that allow you to encrypt elements of arbitrary sets back onto that set. ... and most of them seem to be excessively complicated for what they end up achieving.

Re: Decimal encryption

2008-08-28 Thread Jonathan Katz
On Wed, 27 Aug 2008, Eric Rescorla wrote: At Wed, 27 Aug 2008 16:10:51 -0400 (EDT), Jonathan Katz wrote: On Wed, 27 Aug 2008, Eric Rescorla wrote: At Wed, 27 Aug 2008 17:05:44 +0200, There are a set of techniques that allow you to encrypt elements of arbitrary sets back onto that set. The

Re: Decimal encryption

2008-08-28 Thread Jonathan Katz
On Wed, 27 Aug 2008, Hovav Shacham wrote: - Jonathan Katz [EMAIL PROTECTED] wrote: But he probably wants an encryption scheme, not a cipher. Jon, I'm not sure I understand what you mean. If I am reading his message correctly, the original poster seems to be asking for a

Re: Decimal encryption

2008-08-28 Thread Thomas Baignères
Hello, Actually, block ciphers encrypting blocks of *decimal* numbers exist: - TOY100 [1] encrypts blocks of 32 decimal digits - DEAN18 [2] encrypts blocks of 18 decimal digits - DEAN27 [3] encrypts blocks of 27 decimal digits TOY100 is (almost) broken by the generalized linear cryptanalysis

Re: Decimal encryption

2008-08-28 Thread Greg Rose
One of the earlier messages (I lost it) said that Philipp said that there was information that could be used as a nonce. In that case, I would recommend a stream cipher used to generate 133 bits at a time; if the lump of bits represents an integer in the correct range, add it modulo 10^40...

Decimal encryption

2008-08-27 Thread Philipp Gühring
Hi, I am searching for symmetric encryption algorithms for decimal strings. Let's say we have various 40-digit decimal numbers: 2349823966232362361233845734628834823823 3250920019325023523623692235235728239462 0198230198519248209721383748374928601923 As far as I calculated, a decimal has the

Re: Decimal encryption

2008-08-27 Thread Eric Rescorla
At Wed, 27 Aug 2008 17:05:44 +0200, Philipp Gühring wrote: Hi, I am searching for symmetric encryption algorithms for decimal strings. Let's say we have various 40-digit decimal numbers: 2349823966232362361233845734628834823823 3250920019325023523623692235235728239462

Re: Decimal encryption

2008-08-27 Thread Peter Gutmann
=?ISO-8859-15?Q?Philipp_G=FChring?= [EMAIL PROTECTED] writes: Does anyone know a an algorithm that has reasonable strength and is able to operate on non-binary data? Preferrably on any chosen number-base? I posted a description of how to perform encryption in limited subranges to sci.crypt about

Re: Decimal encryption

2008-08-27 Thread Steven M. Bellovin
On Wed, 27 Aug 2008 17:05:44 +0200 Philipp G__hring [EMAIL PROTECTED] wrote: Hi, I am searching for symmetric encryption algorithms for decimal strings. Let's say we have various 40-digit decimal numbers: 2349823966232362361233845734628834823823 3250920019325023523623692235235728239462

Re: Decimal encryption

2008-08-27 Thread Thierry Moreau
Philipp Gühring wrote: Hi, I am searching for symmetric encryption algorithms for decimal strings. Let's say we have various 40-digit decimal numbers: 2349823966232362361233845734628834823823 3250920019325023523623692235235728239462 0198230198519248209721383748374928601923 As far as I

Re: Decimal encryption

2008-08-27 Thread Greg Rose
Philipp Gühring wrote: Hi, G'day Philipp, I am searching for symmetric encryption algorithms for decimal strings. Let's say we have various 40-digit decimal numbers: 2349823966232362361233845734628834823823 3250920019325023523623692235235728239462 0198230198519248209721383748374928601923

Re: Decimal encryption

2008-08-27 Thread Hal Finney
Philipp Gühring writes: I am searching for symmetric encryption algorithms for decimal strings. Let's say we have various 40-digit decimal numbers: 2349823966232362361233845734628834823823 3250920019325023523623692235235728239462 0198230198519248209721383748374928601923 As far as I

Re: Decimal encryption

2008-08-27 Thread Jonathan Katz
On Wed, 27 Aug 2008, Eric Rescorla wrote: At Wed, 27 Aug 2008 17:05:44 +0200, Philipp Gühring wrote: Hi, I am searching for symmetric encryption algorithms for decimal strings. Let's say we have various 40-digit decimal numbers: 2349823966232362361233845734628834823823

Re: Decimal encryption

2008-08-27 Thread lists
Philipp Gühring wote: I am searching for symmetric encryption algorithms for decimal strings. Let's say we have various 40-digit decimal numbers: 2349823966232362361233845734628834823823 3250920019325023523623692235235728239462 0198230198519248209721383748374928601923 As far as I

Re: Decimal encryption

2008-08-27 Thread Steven M. Bellovin
On Wed, 27 Aug 2008 09:34:15 -0700 Greg Rose [EMAIL PROTECTED] wrote: So, you don't have a 133-bit block cipher lying around? No worries, I'll sell you one ;-). Also see Debra Cook's PhD dissertation on Elastic Block Ciphers at http://www1.cs.columbia.edu/~dcook/thesis_ab.shtml

Re: Decimal encryption

2008-08-27 Thread Eric Rescorla
At Wed, 27 Aug 2008 16:10:51 -0400 (EDT), Jonathan Katz wrote: On Wed, 27 Aug 2008, Eric Rescorla wrote: At Wed, 27 Aug 2008 17:05:44 +0200, There are a set of techniques that allow you to encrypt elements of arbitrary sets back onto that set. The original paper on this is: John

Re: Decimal encryption

2008-08-27 Thread Hal Finney
I like Greg Rose's solution best: There is a fairly standard technique for handling things like this. 1. encode your number N into a 133-bit string S 2. encrypt S with your favourite 133-bit block cipher (see below) 3. decode S to a number N' 4. if N' = 10^40, goto 2 (that is, re-encrypt

Re: Decimal encryption

2008-08-27 Thread Greg Rose
Hal Finney wrote: So, you don't have a 133-bit block cipher lying around? No worries, I'll sell you one ;-). Actually that is easy too. Take a trustworthy 128-bit block cipher like AES. To encrypt, do: 1. Encrypt the first 128 bits (ECB mode) 2. Encrypt the last 128 bits (also ECB mode). I