Emergency Action Message

Note: The contents of this page are unencyclopedic and the article needs to be reworked entirely. Sourced from https://x.com/neetintel/status/1747439860321796519

An Emergency Action Message (EAM) is a highly structured, authenticated message primarily used in the command and control of US military nuclear forces. They disseminated over multiple communication systems including the HFGCS, VERDIN, and satellite systems.

Informational Context

As already posted above, US budgetary documents describe Emergency Action Messages as "highly structured, authenticated messages primarily used in the command and control of nuclear forces. They are disseminated over numerous survivable and non-survivable communication systems including terrestrial and space systems." There are many descriptions of EAMs floating around online and most of them are generally correct – most are 30 characters, etc. – but are generally just recycling the same information over and over, and those descriptions which overreach beyond this tend to become dubious, or in some cases are even demonstrably wrong.

Despite the confidence with which it's declared, the oft-made statement that all EAMs are encrypted using one-time pads (OTPs) is not necessarily correct; not necessarily because there's no source for this statement available anywhere, but because there's decent reason to doubt this. Given messages are broadcast and received by multiple assets globally, and the amount of messages broadcast during any given period does not appear to be necessarily known in advance, etc.... there are several logistical demands that make the feasibility of using OTPs for all EAMs questionable. If you think about the actual needs of the US military for these messages, they don’t actually need them to be OTP encrypted. EAMs are probably time-sensitive messages that even decrypted would probably use abbreviations, codewords, etc. that wouldn't be comprehensible to anyone but the intended receiver(s). So as long as EAMs are encoded in a method that makes them highly resistant to decryption (short of significant compute time/power), the trade-off in not using OTPs for simpler implementation could make sense for them. This is controversial because it upends long-standing accepted wisdom, but I think this only became conventional wisdom because when the shortwave listening (SWL) community, which mostly started off in numbers stations which do use OTPs, discovered the HFGCS, they probably automatically assumed EAMs also used OTPs and never second-guessed this.

While many see EAMs as completely indecipherable, they are (again, as the DoD states) highly structured. Elements of this structure can be readily obvious to anyone who bothers to transcribe them or else can be teased out with a little bit of observation. For example, 100+ character EAMs are often structurally similar to each other based on the specific message length, with repeating tetragrams (e.g. AAAA, BBBB, etc.) in similar positions. 30-100 character long EAMs also have similar structures, but often more obfuscated . Message structure is obvious even for 200+ characters messages.

Trivia that doesn't quite fit into the rest of this article yet;

• At least at one point, EAMs were encoded using a program called EAMGEN.
• From a transcription of a phone conversation available in the DOD archive, @ReidDA discovered that on September 11 2001, an EAM was used to change the DEFCON level.

Structural Features

An analysis of over 6000 unique EAMs to check how often any given letter appears in them shows the letter M appearing significantly less often than any of the other letters. (Generated using eam_characterfreqanalysis_.py)

Rather than EAMs being completely indiscernible and unknowable, collecting these messages and performing basic analysis will actually yield some observations.

• For some reason, the characters M and 5 appear about half as often as any of the other characters.
• For almost all messages broadcast over the HFGCS (8888 messages are an exception), the characters 0, 1, 8, and 9 don’t appear in any of them. The reasons for 0 and 1 are obvious – the numbers 0 and 1 could be confused for the letters O and I (or vice versa). You might think this shouldn't be a concern because messages are read off using a phonetic alphabet, but they’re still occasionally (if not always?) being read off from someone's handwriting, so legibility could be a concern.
• The reason for withholding the numbers 8 and 9 is less obvious, but consider that A–Z & 2–7 = 32 possible characters for an EAM, so it seems reasonable to suggest that EAMs could be using base-32 encryption.
• Some EAMs have strings of identical characters in them, even if they’re broadcast weeks-months apart, if they have the same 2 characters at the start. (Another knock against the idea that we can be confident that they’re encoded using OTPs.)

Speculations, Misinterpretations, and Empirical Realities

As far as the frequency of EAMs and the tendency to associate their broadcasts with "SHTF events";

• EAM broadcast times are not completely random, and they're more often broadcast during daylight hours for CONUS.
• Certain days of the week are typically busier than others.
• While monitoring the HFGCS over the last two years, I heard anywhere from 0 – 50+ messages any given day, with the typical range more like 5 to 25. It's pretty rare for a day to go by without at least 1 EAM being broadcast (when this happens it tends to be on a federal holiday, such as Thanksgiving or Christmas). In line with the typical range I gave, the running average is usually around 15 messages a day.
• Folks will usually stumble on apparent correlations – e.g. if something big happens in Ukraine or the middle east and more than a couple dozen EAMs have been broadcast on the same day, people will take to Twitter and YT and announce a connection. However, people will also regularly overlook days with 30+ EAMs if there's nothing in the news, and vice versa – if there are big news headlines but not a significant amount of EAM traffic, EAMs go undiscussed that day. A strong, consistent correlation between the number of EAMs broadcast and geopolitical events has never been established.
• Are long EAMs cause for concern? At least some long messages appear to be broadcast with a kind of periodicity, and/or tend to be broadcast around the same time as each other. I previously discussed an example of what I mean here on this account, where I explained how there were two instances of a 194 character message broadcast on the third Sunday of a month, and in both instances a 219 character message was broadcast the next day (similarly, I mention how on two Sundays in 2023, a 246 character message and 216 character messages were broadcast around the same time as each other). I've also noticed long messages tend to be broadcast on weekends more often than weekdays. So if some long messages appear to be broadcast in an pre-scheduled fashion to be pseudo-predictable, and geopolitical events don't have quite that kind of periodicity.. whether some correlate to real-world events is still up for debate, but many of them definitely are not.
• Claims that an operator's tone of voice as they read an EAM could indicate the significant of an EAM are completely ridiculous. This isn’t necessarily because it's a question about whether the operator understands the significance of the message, but a mixed track record on the part of the people who make that claim. I’ve seen people claim an HFGCS operator was crying because the EAM they were reading meant that WW3 was about to begin – not only did WW3 not begin (obviously), the operator wasn't crying, they were laughing. Consider that an operator could read a practice message with strong enunciation and a little nervous tremble in their voice not because nukes are about to fly, but because they know a superior who will pass/fail them is listening. Just like anyone else at any job, the mood of an HFGCS operator could be affected by any number of things – personal troubles in or out of work, a funny joke someone just told them, workplace pressure, etc.

EAM Groupings

Need a section with a brief overview of the EAM groups and links to respective pages.

Force Direction Messages

People rarely ask about Force Direction Messages but they probably should do more often, because FDMs are regularly mentioned in DoD documentation in the same breath as EAMs. Though it's unsourced, http://numbers-station.org states that FDMs are probably structured near-identical to EAMs, and we have no way to tell the difference. In other words, what the SWL community and internet does at large – i.e. referring to all these messages as EAMs, might be backwards. In fact, the above section on "What is an EAM?" could be wrong on my part and everything I wrote about observing structures of EAMs, etc. is actually about FDMs. For anyone strictly interested in all this, you might decide that it might be best to talk about all these messages as "EAMs and/or FDMs" (as I sometimes do), but you'll also come to realize that is clunky and pedantic and sometimes colloquial use of a term overrides actual use.

Having said all this, even though it still isn’t possible to tell which one is which, it does appears possible to identify certain 'subgroups' of message types based on the first two characters of messages, which are often reused over certain time periods, but might be acting as differentiating traits. i.e.; somewhat of a lead does exist on differentiating EAMs and FDMs.

See also

Articles.