memcpy(ofb_tmp,ofb_iv,sizeof(ofb_iv));
des_ofb_encrypt(plain,ofb_buf1,64,sizeof(plain)/8,ks,&ofb_tmp);
if (memcmp(ofb_cipher,ofb_buf1,sizeof(ofb_buf1)) != 0)
memcpy(ofb_tmp,ofb_iv,sizeof(ofb_iv));
des_ofb_encrypt(plain,ofb_buf1,64,sizeof(plain)/8,ks,&ofb_tmp);
if (memcmp(ofb_cipher,ofb_buf1,sizeof(ofb_buf1)) != 0)