RDBMS -- ORA-28750: unkown error in SSL web service call

If you are trying to do someting like the following and end up with ORA-28750 error, then the server that you are trying to connect, is probably using an SHA2 ssl certificate.

SQL> DECLARE
2 lo_req UTL_HTTP.req;
3 lo_resp UTL_HTTP.resp;
4 BEGIN
5 UTL_HTTP.SET_WALLET ('file:/wallet/','welcome1');
6 lo_req := UTL_HTTP.begin_request('https://ip_address/erman?wsdl');
7 lo_resp := UTL_HTTP.get_response(lo_req);
8 dbms_output.put_line(lo_resp.status_code);
9 UTL_HTTP.end_response(lo_resp);
10 END;
11 /

DECLARE
*
ERROR at line 1:

ORA-29273: HTTP request failed
ORA-06512: at "SYS.UTL_HTTP", line 1029
ORA-28750: unknown error
ORA-06512: at line

You may think that you wallet is problematic but it is not..
If that 's the case, then you are probably using an older version of Oracle Database :)
Something like 11.1.0.7 maybe... SHA2 is certified in Oracle Database 11.2.0.3 and above.
(To check the certificate you can just save it to your laptop, rename it to .cer then double click on it..)

So if that 's case, then you are two options:

1) upgrade your db ..
2) If the server that gives that web services is on your control, change the server side certificate to be 'GeoTrustSSLCA-G3'

We choose option 1 :) , as it is time.. it is even the time for an 12c upgrade..