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Posted by S. Pidgorny on July 4, 2007, 5:55 am
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good description of RSA, one of the algorithms:
http://en.wikipedia.org/wiki/RSA
It requires some knowledge of math. To put it simply, attacking RSA (and
most other public key algorithms) is little more complex than calculating
prime factors of a huge number. That task is complex (there is a proof of
that - understanding of which requires real knowledge of math, see
http://en.wikipedia.org/wiki/NP-complete).
Alternatively, you can just trust us: if you know public key, you don't know
private, and if you know public key and intercept communication, it's very
hard to recover the plain text.
--
Svyatoslav Pidgorny, MS MVP - Security, MCSE
-= F1 is the key =-
* http://sl.mvps.org * http://msmvps.com/blogs/sp *
> Thanks for the reply.
>
> I understand that these keys have large length hence these are difficult
> to
> crack. Can you give me a simple example regarding 1.
>
> As to what could be a very small private key and veyr small public key so
> that I can see
> - some data getting encrypted by public key
> - the data can not be decrypted using public key
> - the data can only be decrypted using private key
>
> Thanks,
> Tim
>
> "jwgoerlich@gmail.com" wrote:
>
>> The short answer to (1) is that asymmetric encryption requires one key
>> to encrypt and a different key to decrypt. Mathematically, P1 can only
>> decrypt A1 and likewise A1 can only decrypt P1.
>>
>> The answer to (2) is that a utility which derives a private key from a
>> given public key would of course break the system, because then
>> anything could be decrypted. Crypto systems are designed to resist
>> such attacks. There may be ways to do it (reaction attacks against
>> known plain text comes to mind) but they are not much of a risk.
>>
>> Regards,
>>
>> J Wolfgang Goerlich
>>
>> wrote:
>> > Hi,
>> >
>> > If PC1 has public key P1 and private key A1
>> >
>> > and
>> >
>> > PC2 has public key P2 and private key A2
>> >
>> > When PC1 communicates securely with PC2, PC1 will encrypt the data
>> > using the
>> > key P2, which can be decrypted ONLY by using private key A2.
>> >
>> > My question is,
>> > 1. If data has been encrypted using P2 why it can't be decrypted using
>> > the
>> > same key?
>> >
>> > 2. SN.exe generates pair of public and private keys, why can't a
>> > utility be
>> > written which will generate a Private key for a given Public key?
>> >
>> > Thanks,
>> > Tim
>>
>>
>>
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