RSA is an intrinsically fragile cryptosystem containing countless foot-guns which the average software engineer cannot be expected to avoid. Weak parameters can be difficult, if not impossible, to check, and its poor performance compels developers to take risky shortcuts. Even worse, padding oracle attacks remain rampant 20 years after they were discovered. While it may be theoretically possible to implement RSA correctly, decades of devastating attacks have proven that such a feat may be unachievable in practice.

espoofer is an open-source testing tool to bypass SPF, DKIM, and DMARC authentication in email systems. It helps mail server administrators and penetration testers to check whether the target email server and client are vulnerable to email spoofing attacks or can be abused to send spoofing emails.

But while there are many tools to automatically renew certificates for publicly available webservers (certbot, simp_le, I wrote about how to do that 3 years back), it's hard to find any useful information about how to issue certificates for internal non Internet facing servers and/or devices with Let's Encrypt.

This is a different way to learn about crypto than taking a class or reading a book. We give you problems to solve. They're derived from weaknesses in real-world systems and modern cryptographic constructions. We give you enough info to learn about the underlying crypto concepts yourself. When you're finished, you'll not only have learned a good deal about how cryptosystems are built, but you'll also understand how they're attacked.

This page explains use cases and examples of SSH tunnels while visually presenting the traffic flows.

mkcert is a simple tool for making locally-trusted development certificates. It requires no configuration.

If you're setting up a service where people can register their own usernames to be used as a hostname (username.example.com), email address (username@example.com), or URL path (example.com/username) within your domain, there are some common names you should avoid letting the general public register.

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This is a list of all the names I know that should be restricted from registration in automated systems. If you know of others, please let me know and I'll update this page.

The SSH agent is a central part of OpenSSH. In this post, I'll explain what the agent is, how to use it, and how it works to keep your keys safe. I'll also describe agent forwarding and how it works. I'll help you reduce your risk when using agent forwarding, and I'll share an alternative to agent forwarding that you can use when accessing your internal hosts through bastions.

Dangerzone, a new open source tool that First Look Media just released at the Nullcon 2020 hacker conference in Goa, India, aims to solve this problem. You can install dangerzone on your Mac, Windows, or Linux computer, and then use it to open a variety of types of documents: PDFs, Microsoft Office or LibreOffice documents, or images. Even if the original document is dangerous and would normally hack your computer, dangerzone will convert it into a safe PDF that you can open and read.

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When dangerzone starts containers, it disables networking, and the only file it mounts is the suspicious document itself. So if a malicious document hacks the container, it doesn’t have access to your data and it can’t use the internet, so there’s not much it could do.

A lot of the information that gets passed around the Linux community is really good, however, sometimes the information surrounding this topic specifically is not always of the highest quality and it can be difficult to decipher fact from fiction.

In light of the fact that I stand by my previous article, and under the realization that I’m really just some guy on the internet; I thought it would be best to reach out to a few experts and see what they say regarding antivirus software on Linux. I thought it was important that the information I passed on was coming from trusted and well-known vendors in both the Operating System space, as well as the perspective of the antivirus makers, and in that regard I will keep my own commentary to a minimum and let the experts speak for themselves.

Spoiler: For Linux itself, no. For the protection of Windows machines, yes, maybe.