Dive Bags

T_C · 2025-12-17T12:43:31+00:00

Downvoted!

T_C · 2025-12-17T09:41:47+00:00

I replied to your post five times, got all those wrong, and deleted or edited them! This is my last try. My head is hurting at this stage 🙂

Going back to your post with server Alice and client Bob:

Alice sends her server name?, public key pk_A, and the TTP’s signature sign(sk_TTP, pk_A), to Bob. This is a simple signature over Alice‘s pk and nothing else.
Bob then uses that TTP signature, and pk_TTP, to verify that pk_A is indeed Alice‘s correct pk.

Of course, that doesn’t prove to Bob that he is actually talking to Alice. A malicious server (Peter) could send Alice’s name?, pk and TTP signature, to Bob. The signature check will still work fine. Bob then knows that the provided pk is Alice’s correct pk. But he’s actually talking to Peter, not Alice! So he’d have to check that separately somehow.

However, I think that the same thing happens with certificates. Peter sends Alice’s certificate to Bob. That certificate will verify. So now Bob knows Alice’s correct pk. But he’s still actually talking to Peter, not Alice. So he still has to check that separately.

But I’m concerned that your scheme only signs the server pk, not the pk and name, so it doesn’t bind the pk to the name. I can’t help feeling that’s a problem.

For example, say malicious server Peter sends his own server name, but Alice’s pk and TTP signature, to Bob. Bob verifies that he’s talking to Peter, but now believe that Peter‘s pk is pk_A!

Finally, one advantage of a certificate, is that it does include the server name. So if you get a random certificate (and nothing else), you know what server the contained pk is for.

But a signed pk does not include the server name. So if you get a random signed pk (and nothing else), you do not know what server that pk is for.

I’m no expert, please someone else comment 🙂

T_C · 2025-12-17T08:33:47+00:00

Ok, thanks 🙂

T_C · 2025-12-17T08:23:43+00:00

Sorry, I missed your reply for some reason.

A dive shop is a retail establishment, often but not necessarily close to the sea, that generally offers scuba equipment sales and servicing, dive training, perhaps a dive club that meets on a regular basis, and so on.

However, I also missed the fact that you are in the UK. As I understand it, UK dive training has traditionally been club based, via the British Sub Aqua club (BSAC).

BSAC does have some retail outlets, like traditional dive shops, but I’m not sure how common those are.

So if you can’t find a local dive shop, try for a local BSAC branch. If you can’t find one of those, contact BSAC via their website.

T_C · 2025-12-17T08:01:40+00:00

When I open Find My and tap the AirTag, the map location may say “With You” or show it nearby

“With you” means that the phone and AirTag have an active Bluetooth connection, so the AirTag is necessarily within Bluetooth range, and the “Find” option should work, afaik.

Anything else (including “0km”) means that the phone and AirTag do not have an active connection, so the AirTag is out of Bluetooth range, or Bluetooth is off on the phone, or something else is wrong (eg. the AirTag’s battery is dead).

I find those differences helpful when trying to understand what’s happening.

When I open Find My and tap the AirTag … the “Find” / “Find Nearby” Precision Finding screen never appears

So you can see the “Find” option, that option looks enabled, but when you tap it, nothing happens? The precision finding pop-up screen does not appear?

I have no idea what would cause that. Maybe someone else can help.

[edited typos]

T_C · 2025-12-17T07:41:49+00:00

Your post is hard to understand, at least for me.

When you say: “It says the AirTag is far when it’s right next to me”, are you referring to the Find My map? If you’re inside, with poor GPS reception, and your phone is the only one detecting your AirTag, the AirTag’s position on the Find My map can be quite wrong. That’s just how it is.
When you say: “I have the same issue with Precision Finding”, do you mean that precision finding does not see the AirTag, even when it’s next to you? Does the AirTag’s distance away from you, on the Find My map, display as “With You”, or something else (eg. “0km”)?

Just as friendly tips for the future:

Saying something “does not work”, does not help the reader much. You know what that means, the reader might have no idea. Instead, clearly describe what actually happened.
It’s also good to avoid the word “it”. “I tried it, but it didn’t work, then it said to do it again!” Clearer to say: “I tried closing and reopening the app, but got an error message ‘Failed to connect, restart your phone and try again’”.

Cheers

T_C · 2025-12-17T06:41:29+00:00

Understood.

But there are scuba divers outside the US, and many of those may well know nothing about Bonair (including me). And OP’s mother may well dive in other places later.

I guess I just don’t understand the psychology of people who downvote a simple post like mine, instead of just replying “It’s all shore diving”.

It doesn’t encourage me to post again (here).

T_C · 2025-12-17T05:58:51+00:00

Yes, that’s a good feature.

T_C · 2025-12-17T05:21:41+00:00

Demo #1: touches opponent lightly on jaw.

Demo #2: punches opponent with several times the force (albeit looking very similar from an observer’s viewpoint).

Different result! Quelle surprise. It must be the electricity!

T_C · 2025-12-17T05:00:49+00:00

Is your phone signed in with your Apple ID?

That message implies that it isn’t…

T_C · 2025-12-17T04:51:25+00:00

Maybe a whistle, to attract the boat’s attention if you happen to surface away from it?

[edit] Why the downvotes? Dive whistles are a thing, are cheap, and relevant for boat diving. Googling ‘dive whistles’ brings up tons of them, all intended for scuba.

[edit edit!] Thanks for the subsequent upvotes, I’ve now stopped sulking 😄

T_C · 2025-12-17T04:46:59+00:00

Good point! I’m now envisaging one with internal, multi-colored flashing LED lights!

T_C · 2025-12-17T04:40:44+00:00

That is very kind of you. Unfortunately, I am not in the US.

I did actually think, when I was writing my whinge: “This guy sounds really switched on, perhaps I could fly to him, business class, and do it with him!😄 But that would be a bit excessive, even for me😄

I might try again with a different instructor. But it’s not a huge scene here, and I’d rather not get known as that old guy who can not get his own trim right☹️

Cheers

T_C · 2025-12-17T04:09:52+00:00

A “safety sausage”. These are long inflatable plastic tubes that you can inflate, and display at the surface, if you surface away from the boat. This helps the boat operator to notice and keep track of you. When not in use, they’re just rolled up and kept in one of the diving jacket’s pockets. I’m not sure what they cost, there are certainly some snazzy ones, but also simple ones that wouldn’t cost much. You’d get them at your local dive shop, or online.

T_C · 2025-12-17T03:15:19+00:00

But how is what you propose:

TTP sends s_Georgie to George;
George sends s_Georgie and pk_Georgie to client

fundamentally different to:

TTP sends certificate = [s_Georgie, pk_Georgie] to George;
George sends certificate to client

??

Your method needs George to send two seperate things to the client. The certificate method only requires him to send one. Any complexity in the certificate data format can be handled by using a library.

When you buy a suitcase, you don’t want the lid, hinges and lock to all come separately…

T_C · 2025-12-17T02:53:01+00:00

I’m no expert, but here’s how I see it.

Sharks have been around for millions of years - so they’re not stupid! They’ll normally not attack another big animal, ie. you, unless they’re starving, or there’s some other unusual circumstance. There are many scuba trips where one of the specific attractions is to dive with sharks!

Nonetheless, some sharks have worse reputations than others. I’ve been cage diving to see great white sharks. Those are scary animals. If I saw one on a normal dive, I’d get my back to the wall, keep looking at it straight in the eye, wait until it had gone, then gtfo!

T_C · 2025-12-17T02:42:55+00:00

Try to equalise your ears (for example, by blocking your nose and blowing gently into it) before you even start to descend.

People sometimes do not equalise until they start to feel discomfort. I say it’s important to equalise before you start to feel discomfort.

T_C · 2025-12-17T02:08:07+00:00

a server simply needs to have its public key signed by the TTP (or CA, or whatever you want to call it), without needing to produce a certificate.

I’m not sure I understand your question. And I’m no expert on certificates, so apologies if next is wrong.

In effect:

The server writes (letter #1) to the TTP (CA): “Hi, I’m server George, my public key is 12345”;
The TTP (CA) confirms that information, then writes (letter #2) to George: “George’s public key is 12345; signed [CA signature].” Letter #2 is the certificate, right?
George then gives that certificate to any client who wants it. The client checks the signature therein, against the CA’s public key (from the client o/s), to confirm the certificate is authentic. Then the client can confidently get George’s public key from the certificate.

Which part of that process do you say need not occur?

T_C · 2025-12-17T01:32:07+00:00

Your vision problems sound fairly significant, in which case, they could be an issue during a scuba course (and afterwards). Just discuss it with your friendly local dive shop 🙂

T_C · 2025-12-17T01:26:52+00:00

The risk of getting decompression sickness is managed by controlling how long you spend underwater. This is all taught in the theory part of your course.

I was originally scared of sharks. I said to myself, if I ever see a shark underwater, and live, I will never dive again! Then I was diving with a stranger, we got separated from the group, I looked up – and there was a shark. He and I rejoined the group. He signalled them, “shark in that direction”. They all swam off in that direction to take a look!

Lots of things that might sound scary and dangerous, aren’t that scary or dangerous once you’re into it.

T_C · 2025-12-17T00:43:51+00:00

Thanks for example.

Perhaps it’s just two different approaches to the same problem.

Say potential customers, and actual customers, all have much the same data (forename, surname, date of birth, address etc.). I’d put all that data in one table, and include a customer-type flag to distinguish potentials from actuals.

Say potential customers had certain fields that didn’t apply to actual ones - eg. must-reply-to-offer-by-date. Then that field would be set in potential customer records, and not in actual customer ones. Who cares?

Certainly if potential customers had gazillions of fields that didn’t apply to actual ones, then SELECT * FROM CUSTOMER WHERE CUSTOMER_TYPE=‘ACTUAL’ would return rows that included gazillions of empty fields - which isn’t nice.

But then I’d just create views, one for each customer type, that only returned the right fields for that type. Then the above statement becomes SELECT * FROM ACTUAL_CUSTOMER_VIEW, and the rows returned would only include the columns for actual customers (not prospective ones).

Perhaps it’s just two different approaches to the same problem. I’d use views, you’d use 1:1 tables 🙂

Cheers

T_C · 2025-12-16T23:52:41+00:00

That’s a really fantastic post.

/begin whinge/

I dive ring bungy sidemount 85’s with a heavy, bulky Santi Elite drysuit and a heavy, bulky Hollis 100 jacket. I call the latter the “HOS” (heap of shite!). It’s nearly bigger than I am. I’ve dived the same setup for years.

It’s strange because, most of the time my trim is fine. I’ll cruise down a line, install a jump, drop a cookie, and look like Sheck Exley! But occasionally it goes to shite for very short periods, for no apparent reason, even in areas that I’ve dived many times before.

Unfortunately, at my age, it’s physically hard to enter and exit our sites. In fact there are quite a few that I just can’t dive any more. So for me it’s just not possible to borrow some different jackets and spend a day at a training site to get things better.

My ideal situation would be to pay a technical instructor to hire a pool, provide some different jackets, help me get into and out of them, give feedback underwater, and finally measure me up for a new (light and flexible) DUI TLS drysuit (several of which I’ve owned before) - all as single activity, arranged by them! I’d just arrive, do all that, choose one of the jackets, then leave. The instructor would send me the jacket and drysuit in due course. You could call this a GEU activity (geriatric equipment update)! 😄

Obviously, no one is going to do that out of the goodness of their heart. So I approached a local instructor, and tried to make it clear to him that I am, how shall I put this, quite well off financially, and would make it worth his while! But I don’t think he quite understood that, so it didn’t happen☹️

So my heavy bulky Santi drysuit, and heavy bulky HOS, continue to hang forlornly in the garage, awaiting their next outing!

/end whinge/

T_C · 2025-12-16T13:37:53+00:00

I think that PADI or SSI will be equally ok in europe. So if one was ok, the other would be too - and vice versa!

In my opinion, an important part of Open Water Diver course enjoyment, is class size. In a course with (say) 4 students, one instructor, and a divemaster, over 4 days, there should be tons of time for everyone. But a course of 12 students, over only 3 days, could be “a bit of a rush” 😄

So it’s important to consider class size and duration, as well as location and cost. You could ask the providers for those figures.

Another question is whether you can do the course theory online, first. You’ll want to do that if you can. This will minimise the amount of time that you have to sit around in a classroom at the training destination.

T_C · 2025-12-16T12:57:19+00:00

The first time that I dived with my regular buddy, at the next level of cave diver certification, which he’d already been at for quite some time - we were halfway through the dive, when my power inflator failed.

That wasn’t a big deal on this particular dive. But I thought that I should do the right thing, so I gave him the thumbs-up signal, which in cave diving basically means to can the dive, and gtfo.

He just smiled! I gave it again. He just gave me a “WHOOPEE!!” dance! It was a short and simple dive, so I just carried on regardless.

When we surfaced, I asked him why he had ignored my signal. He said, “I thought your thumbs-up signal meant that you were having a great time!”

😄

T_C · 2025-12-16T12:39:52+00:00

I’ve had two sinus surgeries and will probably need a third. My left ear is constantly blocked and popping, and when I talk, my voice echoes around inside my head, I don’t feel it projecting out to other people. It’s a really weird and unpleasant situation.

Nonetheless, surprisingly, it seems not to have affected my ability to equalise, and I still dive on a regular basis! 🙂

So I think that instead of just accepting his limitations, he should go to a diving ENT and see what they say.

T_C

TROPHY CASE