Decimal encryption

[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 original paper on this is:
>>> John Black and Phillip Rogaway. Ciphers with arbitrary ?nite domains. In
>>> CT-RSA, pages 114?130, 2002.
>>
>> But he probably wants an encryption scheme, not a cipher.
>
> Hmm... I'm not sure I recognize the difference between encryption
> scheme and cipher. Can you elaborate?

A block cipher is a primitive that can be used, in particular, to 
construct encryption schemes. But you can construct encryption schemes 
without block ciphers, and you can use block ciphers to construct other 
things besides encryption. Moreover, "good" encryption should generally 
be randomized, while a block cipher is deterministic.

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