DES_ofb_encrypt
LCRYPTO_ALIAS(DES_ofb_encrypt);
void DES_ofb_encrypt(const unsigned char *in, unsigned char *out, int numbits,
LCRYPTO_USED(DES_ofb_encrypt);
DES_ofb_encrypt(plain,ofb_buf1,64,sizeof(plain)/8,&ks,&ofb_tmp);
DES_ofb_encrypt(ofb_buf1,ofb_buf2,64,sizeof(ofb_buf1)/8,&ks,&ofb_tmp);