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I'm an engineer with experience in applied cryptography, in particular in Smart Card systems.


Nov
19
comment Is there a way to systematically calculate the public exponent $e$ in RSA?
You means $40 = 2^3\cdot5$. This method involves factoring $p-1$ and $q-1$ (and choosing a small odd factor not appearing in this factorization). By hand, this is utterly impractical for even moderate $p$ and $q$. Try it with $p=14627, q=15959$. Then compare to the method I'll add in my giant answer.
Nov
19
comment Simple encoding function mapping integers
The first integer likely is The Answer. The second likely is $\big\lfloor {18\over25}x-44\big\rfloor$ where $x$ is the input. The rest is left as an exercise to the reader.
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
Better justufication that the teacher's algorithm is safe, despite leaking information
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
Again remove the same repetition; was there some caching issue? Comment on the method used by the teacher.
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
reformulate condition for e=N to work
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
Clarify
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
remove a repetition
Nov
19
comment Where have all the cypherpunks gone?
@Nils Pipenbrinck: yes, but the traffic on sci.crypt (URL: news:sci.crypt or news//:sci.crypt ) has lowered, and I now seldom read something interesting. I am 100% bought by the editing capabilities and relatively high quality of the material we get here. My main fear is about long-term archival, but that's for meta.
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
e=N is not suitable in the example of the question
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
use \phi rather than \varPhi
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
Beautify
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
Polish
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
Justify that e=N is safe
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
Polish
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
e can also be random and not necesarilly prime
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
Nearly full rework, giving a straight constructive method
Nov
19
revised Is there a way to systematically calculate the public exponent $e$ in RSA?
Nearly full rework, giving a straight constructive method
Nov
18
answered Is there a way to systematically calculate the public exponent $e$ in RSA?
Nov
18
comment Java RSA/ECB/PKCS1Padding encryption with .NET
$e=2^{16}+1=65537$ (which is most usual), but it is encoded in decimal, then ASCII (giving the string "65537"), then a variant of Base64 without final =, which is byzantine. The value given for $n$ starts in the same ugly format, then (in the XXXX segment) deviates from it, thus is unusable; that might be some of your problem. $\;$ Not knowing your cryptographyService, we can't guess what's the format it wants; and that's off-topic of crypto.SE, as well at what's exactly the format output by RSACryptoServiceProvider.Encrypt (and you give no example of either).
Nov
18
comment Malicious DH groups
It is not clear if you want $p$ to be a 2048-bit safe prime (meaning $q=(p-1)/2$ is 2047-bit prime); or $p$ to be prime with $p-1$ divisible by a much smaller prime $q$ of specified size, e.g. 256-bit. The two are exclusive. In either case, the question is interesting, and I can't answer. $\;$ Also, it might not be quite the same to be able to solve the DLP, and break some protocol that is no safer than the DLP is.