我正在尝试构建一个openssl简单程序。这是完整的代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "openssl/aes.h"

int main(int argc, char* argv[])
{
    AES_KEY aesKey_;
    unsigned char userKey_[16];
    unsigned char in_[16];
    unsigned char out_[16];
    strcpy(userKey_,"0123456789123456");
    strcpy(in_,"0123456789123456");

    fprintf(stdout,"Original message: %s", in_);
    AES_set_encrypt_key(userKey_, 128, &aesKey_);
    AES_encrypt(in_, out_, &aesKey_);

    AES_set_decrypt_key(userKey_, 128, &aesKey_);
    AES_decrypt(out_, in_,&aesKey_);
    fprintf(stdout,"Recovered Original message: %s", in_);      
    return 0;
}

我尝试使用以下命令进行编译：

gcc -I/home/aleksei/openSSL0.9.8/include -o app -L . -lssl -lcrypto tema1.c

我得到这个：

 /tmp/ccT1XMid.o: In function `main':
 tema1.c:(.text+0x8d): undefined reference to `AES_set_encrypt_key'
 tema1.c:(.text+0xa7): undefined reference to `AES_encrypt'
 tema1.c:(.text+0xbf): undefined reference to `AES_set_decrypt_key'
 tema1.c:(.text+0xd9): undefined reference to `AES_decrypt'
 collect2: ld returned 1 exit status

我在Ubuntu 10.04下。我怎样才能使它工作？