newbie troubles to use avrcryptolib

i try to add Triple-des encryption in my webserver which follow etherShield lib.

the encryption and decryption lib i use is the avrcryptolib form
http://avrcryptolib.das-labor.org/trac/wiki/Getting

i'm newbie. do not know how to add this lib into arduino libs,so i just copy two files des.h and des.c into the same folder i placed
etherShield_webserver.pde.

and i get this

o: In function print_webpage(unsigned char*)': C:\DOCUME~1\SUNJH_~1\LOCALS~1\Temp\build6893554923546906212.tmp/etherShield_webserver.cpp:201: undefined reference to des_enc(void*, void const*, void const*)'

the codes i added into etherShield_webserver.pde

uint16_t print_webpage(uint8_t *buf)
{.....
unsigned char PROGMEM DesCryptographicKey[]      ={ 0x12,0x34,0x56,0x67,0x89,0xab,0xcd,0xef };
unsigned char PROGMEM DesPLAINTEXT[]            ={ 0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08 };
unsigned char PROGMEM DesCIPHERTEXT[]            ={ 0xf2,0xac,0x1b,0xc6,0xbf,0x00,0x61,0xd3 };


unsigned char DesKey[8];
unsigned char DesPlain[8];
unsigned char DesCipher[8];
memcpy_P(DesKey,DesCryptographicKey, sizeof(DesKey));
memcpy_P(DesPlain,DesPLAINTEXT, sizeof(DesPlain));
memset(DesCipher,0,sizeof(DesCipher));
//the codes above were borrowed form des_test.c in emsign's 
//avrcryptolib(http://www.emsign.nl/)


des_enc(DesPlain,DesCipher,DesKey);
.....
}

how could i make it right?thanks

P.S .
i am confused with another avrcryptolib form http://www.emsign.nl/
In this lib codes were written in asm ,how to use this lib?

Did you add

#include "des.h"

to the sketch?

PualS ,Thank you.

I did add the line.

#include "des.h" in sketch.

Since you are trying to use a C function in a C++ program, you may need to add:

#ifdef __cplusplus
 extern "C" {
#endif

and

#ifdef __cplusplus
}
#endif

to the .h file, at the top and bottom.

PualS ,Thanks for your help.
follow your order,the problem solved.