i2d_ASN1_INTEGER
penclen = i2d_ASN1_INTEGER(pub_key, &penc);
dplen = i2d_ASN1_INTEGER(prkey, &dp);
penclen = i2d_ASN1_INTEGER(pubint, &penc);
dplen = i2d_ASN1_INTEGER(prkey, &dp);
priv_len = i2d_ASN1_INTEGER(asn1key, &priv_buf);
int i2d_ASN1_INTEGER(ASN1_INTEGER *a, unsigned char **out);