how to use libgcrypt library

Neil Spring
Thu, 24 Jul 2003 21:58:30 -0700

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I don't know what operating system you're using.  And I don't know how  
to solve your linking problem; perhaps it is solved by running "ldd  
./sig_neil" and if it doesn't find libgcrypt, setting the  
LD_LIBRARY_PATH environment variable to /usr/local/bin.

And what you copy in your message is the expected output of the dinky  
test program -- the s-expression that includes the signature dumped to  
the screen.  It is not useful output, just enough to demonstrate that a  
signature was constructed.  You'll have to figure out how to use that  
value, presumably using the gcry_mpi_* functions to extract it in a  
convenient form, in whatever data you sign.  Using the gcry_sexp_dump()  
function to print all of them out helps to understand how data flows  
through the program.

If you are a beginner with encryption, a few posts ago mentioned the  
handbook of applied cryptography at ( ).  Of course, gcrypt still lets  
novices (including me) write insecure systems, so knowing what you're  
doing and why is important.

good luck,

On Thursday, Jul 24, 2003, at 21:04 US/Pacific, Zen wrote:

> Neil,
> Thanks for your help again. Your programe is very useful, and it can  
> work well.
> I have a question when i want to use it out of libgcrypte library. I  
> named it sig_neil.c temporarily. It can be compiled, my compile  
> command : 'gcc sig_neil.c -g -O2 -Wall -o sig_neil -L/usr/local/lib  
> -lgcrypt -lnsl ', but its runing message: 'error while loading shared  
> libraries: cannot open shared object file: No such  
> file or directory.'
> In /usr/local/lib and ./ directory, there has file  
> ,which is a link file.
> Whether my compile command is incorrect? What it should be?
> By the way,in the inner of libgcrypte library, i modified original  
> Makefile, then 'make',
> run './sig_neil',its runing result is correct, but its output has:
> not enough random bytes available (need 268 bytes)
> please do some other work to give the OS a chance to collect more  
> entropy
> [open]
>   [data="sig-val"]
>   [open]
>     [data="rsa"]
>     [open]
>       [data="s"]
> [data="\x12\xbf\x04\xe85\x8d\x8a0u|\xf1\xa3I=H\x95hS\x9bR\xd8\xd3r\x9a\ 
> x1e=\xa1%\xa7\xe1\xb4L"]
>     [close]
>   [close]
> [close]
> What's it mean? Can i look it over?
> I am a beginner in the filed of encrpytion techniques, so i am very  
> sorry for my questions may be very childish. I wish they will not  
> waste your too much time.
> Thanks for your help.
> Best regards,
> Zen.

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