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Digicert revokes a raft of web security certificates – Naked Security

Here’s a bureaucratic nightmare that unfolded over the weekend

Digicert is one of the Big Five commercial CAs, short for certificate authorities – companies that sign and vouch for the digital certificates that put the the S in HTTPS and the padlock in your browser’s address bar.

As we’ve mentioned before, web certificates and HTTPS (secure HTTP) aren’t just about protecting you from surveillance by encrypting the data that flows between your browser and the websites you visit.

They’re refered to as certificates rather than just encryption keys because they provide some sort of assurance that the people running the site you’re reading have some sort of authority – for various interpretations of the word “authority” – to do so.

Note that the certificate doesn’t vouch for the safety or the accuracy of the content on the site, so cybercriminals who set up their own sites can acquire certificates for those sites. But the web certificate system does make it harder for crooks to set up imposter sites using existing website names.

The simplest form of web certificate is called self-signed, and anyone can create a self-signed certificate in seconds that claims to represent any web property they like.

Here, we’ve used OpenSSL, via a simple series of Lua script commands, to produce a public/private keypair, put the public key into a web certificate, make the certificate valid for 7200 seconds (two hours), and set the certificate to be authoritative.

In the last line, we self-signed it with the private key we generated up front:

We ended up with a private key that we can use to set up HTTPS connections, plus a certificate to send to the other end to vouch for our website, tied cryptographically to our own private key:

As you can imagine, no browser accepts self-signed certificates directly from websites by default – by replacing the text string example.test in the code above, we can generate a self-signed certificate in any name we want, valid for as long as we like, so self-signed certificates provide no authentication at all.

Using the code above, running in a loop on a single core of a five-year-old laptop, we generated more than 800 256-bit elliptic curve private keys and web certificates per second. 3072-bit RSA keys, which provide similar security levels to 256-bit elliptic curve keys, are much slower to create, limiting us to about three certificates per second per CPU core.