I had problems to resolve and retrieve artifacts from an IBiblio Resolver. I was behind a corporate proxy and even if this proxy was correctly configured in Ivy, I was permanently denied access.
After looking at the HttpClientHandler source code, I found that this was due to a lack of support for NTLM authentication. So I added this behavior in the submitted patch trying not to break the original behavior.
Now, Ivy supports NTLM authentication if -Dhttp.proxyRealm=<your_domain> is set in ANT_OPTS. I could not test Basic Authentication but it seems to work also. Maybe someone can confirm ?
Moreover, in order to avoid breaking an old bug, I put NTLM AuthPolicy after the Basic one in the list authPrefs to make it of less priority during the scheme selection.