I had a card like a credit card that I used to use for work. It was an ID card, and it had an access code, a swiper, a barcode, my picture, my name, my rank, my license, the name of the company, and the address of the building where my companies data center was. It was plastic, and was multiple colors.

My method:

  1. SHRED; I used a cross cut shredder first
  2. CUT; I cut it into smaller pieces
  3. MELT; I then melted the card on my stove. I wore a gas mask. At the end of this stage, the plastic curled up on itself, and all color was gone, with only a black and some brown on the inside.
  4. SMASH; I took a hammer and smashed it into tiny pieces.
  5. GRIND; I then used my palms to grind it until it was just black dust
  6. FLUSH; I flushed it down the sink. I do not use a septic.

My question: is there any way someone who was not authorized to enter the data center could use my access card to enter?

  • 1
    You probably didn't need to do any of that. Your employer should have revoked that card's access as soon as it was no longer authorized for use. Dec 7, 2022 at 19:18

2 Answers 2


Physical destruction of a card like that is likely unnecessary.

Assuming this is a simple magnetic stripe or RFID card it will just hold an access code (probably in addition to the same info printed on the card). It is just a way to authenticate you, like a password. Your employer's systems determine what someone presenting that code is allowed to do (i.e. which doors you can unlock).

Assuming you no longer work for that employer (or even if they just issued you a new card), they will disable your old card's access to their systems and facilities as a matter of course.

  • So, just to make sure I am understanding this, the card was useless anyways, and even if the card was reassembled then it wouldn't grant access? Dec 7, 2022 at 19:55
  • Correct. It's just like if you had a physical key and after you left they changed the locks. The key is now useless. Dec 7, 2022 at 19:58

It's not the card itself that matters, but the info (authentication data) that it carries.

Every time you used the card to gain access to whatever you are supposed to, the card's data had to be somehow compared with another copy of the data (probably stored somewhere, accessible by an authentication system) in order to authenticate you.

With all the steps you took, it should be impossible for anyone to reconstruct any part of your card and make any use of it (I would expect that they required you to return the card to the company, but that's another story).

But, by destroying your card, you destroyed your own copy of your authentication data; if the company hasn't taken its own steps in order to invalidate/delete your authentication data from their systems, an attacker could steal/copy the data, create a new card and impersonate you.

However, that shouldn't be your problem.

  • They said I could return the card and they would destroy it or I could destroy it using "appropriate measures" if I recorded the whole process and was supervised Dec 7, 2022 at 20:09
  • @Agoogleworker the key point here is that they should disable/delete your access from their side. If they did this, then even if you kept your card it wouldn't matter much (only to reverse engineer the card and try to figure out a way to break in, but I don't think that would be of much value when it comes to protection measures entailing physical security)
    – user284677
    Dec 7, 2022 at 20:15
  • oh, I see. So it's not that the card is destroyed, but it is that the card doesn't work. Destroying it doesn't matter. Dec 7, 2022 at 20:22
  • @Agoogleworker yes - imagine if you were able to copy the card somehow, you destroyed the original card as requested, the company did not disallow your access and you used the copy-card; you would still have access. If they disable your account/credentials/authentication data, then even the original card cannot provide access to anything
    – user284677
    Dec 7, 2022 at 20:28
  • @Agoogleworker security and usability always go against each other; the more secure, the less usable and the more usable the less secure
    – user284677
    Dec 7, 2022 at 20:38

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