by jake

What is the meaning of MSD in relation to OpenPGP/GnuPG/PGP?

Have ever wondered about the strongest set of connected keys?

keyanalyze can show you some interesting statistics involving the strong set.

The original work was started on dtype but for various reasons, it stopped running.

The project has been taken over and is running bi-monthly on

What is this madness?

A measuring exercise?

For some, yes.

An example: To look at my key I must find it. As of this current publishing, I am not in the top 1000, so I must download the current file.

Then with handy grep I can see this result:

$ grep 2FE875CC msd-sorted.txt
3237 D7CA3ABA 2FE875CC 5.0460

This shows that my key has an MSD of 5.0460. Thus my key is number 3237 of the strongly connected set.

What does this mean?

From The "strong set"

This analysis focuses on the web of trust, and in particular something called a "strongly connected" set. Consider that every key in the world is some point in a graph. Signing another key creates a one-directional edge/vector from the 'signer' to the 'signee'. A strongly connected set is one in which one can follow these edges from any point in the set and get to any other point in the set.

A measure of trust

There are a variety of metrics one could apply to this set, but I've chosen initially to measure the "mean shortest distance" (MSD) to each key. Since every key is reachable from every other in the strong set, it is possible to find out the shortest distance (number of hops) to any given key from any other key. Averaging these distances gives the MSD to that key from every other key in the strong set.

It is desirable to have as short as possible an MSD to your key, as that means that on average, people can reach your key quickly through signatures, and thus your key is relatively more trusted than a key with a higher MSD.

NOTE: This does not mean that you should universally trust keys with a low MSD. This is merely a relative measurement for statistical purposes.


You could also measure the MSD from a given key to every other key out there. This would give some measure of how close you are to others. While this is potentially valuable, it potentially has the very dangerous drawback of encouraging frivolous signatures. I could sign every key on the net and make myself the best "signer" in the world, but this would only serve as a circumvention of the system. This is why I only measure MSD to a key, rather than from it. This properly encourages verifying yourself to others. Signing others' keys is still very important, as it increases your personal web of trust.

You can look up keys on this server as well, then check for them in the latest measure and you can submit them as well.

You can see the top 50 keys as well as the top 1000 keys on the web without decompressing.

So go to a keysiging party and build your web of trust.


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