[botan-devel] Questions of Botan Crypto Library

Sharada Acharya Sharada_Acharya at persistent.co.in
Thu Apr 26 06:24:17 EDT 2012

Hi ,

I am using the Botan crypto library for the purpose of FPE. I ran sample application of FPE given in the examples.
I have few questions regarding the FPE implementation -

1)      Does this FPE implementation support string data or is the support limited to numeric data only ?
If it doesn't provide the support for string data, is it possible to write an application on top of this library which will add support for the same ?

2)      In the standard FPE specifications, it is mentioned that the length of the input text and the cipher text is same, i.e. length is preserved.

On the contrary, I found that Botan FPE gives a cipher text which is of different length than the input text. Is this behavior expected ?

3)      In the sample program of FPE (doc/examples/fpe.cpp), it seems that the length of cipher text depends on the parameter 'n' (first argument to fe1_encrypt). Length of the ciphertext always comes out to be equal the length of 'n', irrespective of the length of the input text. As per the documentation, it encrypts X modulo n, where X is input number. I tried running the program by changing the values of 'n'. When n=1, the program crashes. The length of the output is also not consistent when the value of n = 3.  Can the value of 'n' be used as the configuration parameter for length of ciphertext ?

Could you please provide answers to the above questions ?


Sharada Acharya

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