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I've made a list of the services/devices that require a PIN code. Shockingly, it's over 10, which I find impossible to remember, so I need a strategy to reuse the codes.

What could be a strategy for doing it in the most secure way?

Devices that require a PIN:

  • Bank card
  • SIM card
  • Smartphone
  • Hardware security key

Services that require a PIN:

  • Messaging apps (like Telegram)
  • Banking apps

The challenge is that there can be multiple of these devices/services.

Edit: Having read the insights provided in the comments, I realized this is quite a complex issue and I need to think more about it. I marked an answer, but will edit or open a new thread if there seems to be other solutions.

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    I'm not sure there is a secure way to reuse secrets (PINS, password, etc.). Once one is exposed, then the rest are compromised. Are you wanting to know how to reuse them or do you want to know how to manage PINs?
    – schroeder
    Mar 25, 2023 at 11:09
  • Only 10 or so? I have had about 50 to remember for more than 10 years when you include burglar alarms and combination padlocks. You just get muscle memory.
    – Chenmunka
    Mar 25, 2023 at 11:41
  • Probably I'd like to know how to manage many PINs by reusing them, if that makes sense. Secure reuse might not be possible. However, maybe the effect of a reused PIN being compromised could be lowered by e. g. using the same PIN only on different physical devices, or mixing two codes to create a third. Mar 25, 2023 at 11:58

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I've noticed that PIN codes are pretty much always stored in plain text (support staff might even tell you your code), so sharing should definitely be avoided.

Instead, use a password manager. Any service for which you don't need to enter a code regularly should get a random code of the maximum allowable length (which might be four).

Codes you enter regularly should be as long as you're comfortable with but should not be recycled. Armed with your phone's password manager, your repetitive use of them should eventually train your memory.

If you need help memorizing the codes, consider the Major System or similar (that link has two more). This lets you transform the number into a word or phrase. To further help memorize, you can associate that word/phrase with a familiar place since the human mind is quite adept at remembering locations.

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    Thank you. I realized the problem is more complex than I thought. As you mentioned using a pw manager, differentiating by frequency of use, and smart memorization should help. Also maybe differentiating by importance and physical devices could help, but here it just get too complex for me at the moment. Mar 28, 2023 at 21:57
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Any reuse increases the risks of compromising other accounts/devices. Thus your question contradicts to itself and cannot be answered.

But if your question actually is "How to store multiple PINs securely?", then one of solutions can be a password manager. It is not automatically better. You just trade one set of risks to the others.

An advantage is that you can store a practically unlimited number of PINs and they are all independent on the others. You don't have to reuse any of them. If anyone sees how you enter a PIN for some account/device, all other your accounts/devices remain safe, because you don't reuse PINs.

On the other hand, you need to consider the risk of compromising the device where you store the PINs or where the password manager is running, and the risk of compromising the password manager app.

If you consider these risks as acceptable, this can be a solution. We cannot tell what is acceptable for you. Only you can decide.

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  • A password manager indeed seems like a good tool. Mar 28, 2023 at 21:58

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