Jeremey Barrett <jeremey@forequest.com> writes on cpunks:
[...] But since a one-way hash function (implemented as a one way function) can't really be used for encrypted communication,
One way hashes can be used to produce an block encryption system running in CFB mode, eg: Peter Gutmann's MDC. (CFB mode is where you encrypt an IV (just a random salt) with the key, and XOR the result with the data (you chaing the encrypting for subsequent blocks) -- to decrypt you just repeat the process, use the same IV and encrypt again. As you never actually use the block ciphers decrypt function, you can therefore (and this is what MDC does) use a one way hash in the place of a block encryption algorithm in CFB mode.)
I don't think it is subject to export restriction.
They don't seem to be subject to export restrictions, but then perhaps that is paradoxical, perhaps they should be. (Well no crypto should be export restricted in my view naturally, but for logical consistency you understand...) It would in my view be a good thing if one way hash functions were declared to be non-exportable, as this would clearly hinder commerce, as they are used in signatures and authentication. Also I seem to remember that Dan Berntstien's case was based on the prior restraint in him not being free to discuss his method for turning a one way hash into a symmetric key function. Adam -- Exported RSA today? --> http://www.dcs.ex.ac.uk/~aba/rsa/ #!/bin/perl -sp0777i<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<j]dsj $/=unpack('H*',$_);$_=`echo 16dio\U$k"SK$/SM$n\EsN0p[lN*1 lK[d2%Sa2/d0$^Ixp"|dc`;s/\W//g;$_=pack('H*',/((..)*)$/)