Q: safari can't establish a secure connection

The problem is not limited to Safari - it is computer-wide. Chrome also fails, as does wget from the terminal. I disabled IPv6 and the problem resolved.

I was working on a site I manage at the time, and I have asked for help to ensure that the Website and all its constituent components - AT&T firewall, Akamai, lots of intermediate actors - are fully IPv6 enabled. This is going to be an on-going problem for us all over the next few years as we transition to more and more https and more and more IPv6 - getting all the gears aligned will take time and consternation.

Thanks seeburg220. I was having a problem just with one website. From your post I was able to quickly discover that Avast Web shield was the problem.

All I had to do to was go to Avast > Preferences > Shields > Web Shield > Settings, then under Excluded servers add the url of the site it wasn't giving me access to. Job done!

My problem is with Safari and only with Google sites, e.g. Google search just hangs showing a blank page. It happens either when the mac has been asleep or if the underlying internet connection was reconnected for example if the ADSL modem needed restarted but not the airport extreme thus WiFi stayed connected. I believe it is a bug in Safari's DNS caching affecting the SSL connection not being re-connected perhaps because Google's IP changes due to their load balancing when either of those things happen, and perhaps Google is not allowing the original SSL connection to be reconnected to its new server IP. Or it could be an SSL certificate problem. Either way Safari has the bug since other browsers are not affected.

I was having the same problem. I have spent the last day trying to find the right resolution. I found a link to another forum and they recommended that you delete the ~/Library/Preferences/com.apple.security.plist file. I did this restarted Safari and everything was back to normal.  Please note that I was able to access all of the google sites using Chrome or Firefox. On my macbook air everything worked fine accessing google from safari. It was just my new mac book pro that was having an issue.  I hope this helps.

I haven't had the problem for a while now and I'm pretty sure I fixed it by doing this:

In Keychain search for Geotrust Global CA, mark it "never trusted" close it enter password to save, then mark it "Use system default" and close it and save again. This is the CA that google use for its certifications. You can confirm it by clicking the padlock in the Safari address bar when at google.com

I learned the solution from this Danish guy who had the exact same problem but with Twitter, so he had to do it to the Verisign CA instead.

This doesn't always fix this issue. I deleted all my certificates and then reloaded them (I use PKard to do this). I still can only access certain PKI-enabled SharePoint sites and others fail to load ("could not establish a secure connection.").

I thought this was a likely explanation as well...but it doesn't explain why I can still access certain PKI-enabled MS SharePoint sites from my iMac and not from my MBP.

I access two US Government PKI-enabled MS SharePoint sites, both administered by separate domains. I am able to access both MS SharePoint sites on my iMac - yet when I try to access both from my MBP, only one is accessible. So I think it is safe to assume that security protocols are not the issue with me. Both Macs are running the latest OS X are up to date.

I have had numerous problems with getting PKI certificates to work properly on my MBP. My issue is that I am using PKard to install US government PKI certificates from a CAC onto my Mac - I use both a MBP (late 2012) and an iMac (mid 2011). Up until a couple of weeks ago, I had no issues. Both Macs are running the latest software updates from Apple.

But now my access to certain PKI-enabled MS SharePoint sites is failing. Not blocked - Safari just tells me that the secure connection has failed. I access multiple PKI-enabled MS SharePoint sites, they are each controlled by separate domains. And it is only one MS SharePoint site that fails to establish a secure connection, the other loads without any issues. To make matters even more confusing, this is only happening on my MBP, access to PKI-enabled MS SharePoint sites from this one domain is working just fine on my iMac.

I did get a new CAC at roughly the same time as the problems were occurring. But in the past this has never presented itself as a problem - I automatically delete my PKI certificates from Keychain Access and then reload them using the PKard Assistant (see below). I am sure I am missing something with this - but I am at a loss as to explain what it is exactly as I can still access this particular domain's PKI-enabled MS SharePoint sites from my iMac.

Both Macs access the Internet via my home wi-fi. I tried accessing the Internet via a hard line to the modem (CAT5 cable) with both Macs, the problem repeats itself. I also access the Internet on occasion via a tethered connection to my iPhone 6s Plus. The problem repeats itself there as well (I did test this by tethering both my MBP and iMac).

- I don't think this is due to Apple pushing some sort of security update - as I can access the PKI-enabled MS SharePoint site on my iMac. This would be a possibility if it was occurring on both Macs. Same goes on the SharePoint side - I have spoken (via email) to the admins for the site I am having issues accessing, there is nothing wrong with my permissions. Also, my PKI certificates work fine with Outlook Web Access (OWA).

- I have added the specific domain to ClicktoPlugin and Ghostery. I have also tried disabling them entirely as well, neither worked (ClicktoPlugin should be interfering, but I figured why not try this).

- I have disabled GlimmerBlocker entirely. This had no effect.

- I have created a rule to allow all connections from the domain in Little Snitch, as well as disabling it entirely. This had no effect.

- I disabled IPv6 via the Terminal, for both Ethernet and Wi-Fi. This had no effect.

- I disabled each component of Intego VirusBundle X8, and also uninstalled it completely. This had no effect.

- I have deleted and reloaded my PKI certificates from my CAC using PKard. This had no effect.

- I have turned off and turned back on the Mac Firewall. This had no effect.

- I have deleted all Safari security preference files ( ~/Library/Preferences/). This had no effect.

- I followed a recommendation in this thread (      Link to this post     ) about setting certain certificates to not trusted, trusted, system defaults, nothing worked. I also did this for my US government PKI certificates, same failure to establish a secure connection.

Any help would be appreciated. I use my MBP for work (I don't always have access to a US government computer), and need only to access OWA and MS SharePoint sites. It is a pain to have to drive home (1/2 hour drive) just to send an email or update a SharePoint site.

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Deleting the Cache.db file and removing all website data didn't work. The Firewall doesn't seem to be affecting the site - I have turned the firewall off and tried to access the site, and it didn't work.

I have exactly the same problem.  None of the fixes work and I sooooo fed up with Apple.

This really helped! thanks!

I have Avast installed. Turning off web protection solved the problem.

Open safari > safari preferences > general > set safari opens with new window .

you must have enabled as :  A new private window that is private browsing .

And in private browsing cookies are disabled , to run Facebook cookies must be enabled .

An article for private browsing is there : Safari 8 (Yosemite): Use Private Browsing windows

The person you are addressing hasn't been active here for about 2 years.