For example, would a question asking what the Blowfish structure BLOWFISH_CTX or the variables xl and xr do in the following header does be on topic here?

blowfish.h:  Header file for blowfish.c

Copyright (C) 1997 by Paul Kocher

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

See blowfish.c for more information about this file.

typedef struct {
  unsigned long P[16 + 2];
  unsigned long S[4][256];

void Blowfish_Init(BLOWFISH_CTX *ctx, unsigned char *key, int keyLen);
void Blowfish_Encrypt(BLOWFISH_CTX *ctx, unsigned long *xl, unsigned long *xr);
void Blowfish_Decrypt(BLOWFISH_CTX *ctx, unsigned long *xl, unsigned long *xr);

Or would that belong at SO or CR.SE?

  • 1
    $\begingroup$ Please ask programming related on SO. Crypto.SE focuses on the mathematical models behind cryptography. $\endgroup$ Aug 30, 2013 at 20:58
  • $\begingroup$ @HendrikBrummermann That's why I thought that more people at Crypto.SE might know about what xl and xr are supposed to be. $\endgroup$ Aug 31, 2013 at 6:49

1 Answer 1


Such a question should be asked on Stack Overflow.

As the help center says:

If your question is about using a cryptographic library (e.g. Crypto++, OpenSSL etc) and using it in your application, you probably need Stack Overflow. (A good indicator is the existence of source code in your question or most good answers).


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