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Discussion about OpSec, Threat Models, Protection, Assessment and Countermeasures.

Fingerprints on paper?

by /u/somuchonmymind · 4 votes · 1 week ago

Hi,

is there some way to clean fingerprints from paper after you touch it?

Since you can't use alcohol on paper surface. Any ideas?

Thank you

Comments (9)
/u/fall · 4 votes · 1 week ago · Link

burn the paper lol

/u/ThePanther · 3 votes · 1 week ago · Link

Fingerprints on normal paper (cellulose paper) are made visible by using a chemical substance called Ninhydrin. This substance reacts with the amino acids that are absorbed by the paper if the contact from the skin with the paper was long enough (at least 6 - 8 seconds!). This creates a red-violet dye called Ruhemann's purple. Amino acids are very common in nature. So it would be enough to contaminate the paper with an amino acid solution (for example egg white dissolved in water). This would discolor the entire paper when examined.

But this method is of little use, however, since Israeli researchers succeeded in reversing the process a few years ago. They do not color the fingerprint, but the paper that has not been in contact with the skin secretions. They use nanoparticles from gold, which adhere to the surface of the untouched paper. These areas are then colored black using silver ions, which means that the fingerprint is shown as a negative (white on black background).

How about wearing gloves?

Or remove your fingerprints?

/u/KAVe · 2 votes · 1 week ago · Link

Man where do you learned that lol

/u/SlowLorus · 1 votes · 1 week ago · Link

Ha...and this is why I love Dread!

/u/ThePanther · 1 votes · 1 week ago · Link

When I was 3 years old, my parents gave me a chemistry kit... ;-)

/u/somuchonmymind OP · 1 votes · 1 week ago · Link

Thank you for interesting answer.

Do you think one layer of nitrile gloves is enough to not leave fingerprints?

Also i would like to ask, how long should you wear one pair of gloves? How often you should change it for new? Thanks!

/u/ThePanther · 1 votes · 1 week ago · Link

As long as the gloves keep the secretions of the skin (mainly sweat and grease) away from the paper, even gloves made of fabric are sufficient.

I think it's always a question of relativity. So the question of what the reason for the law enforcement investigation is. And of course in which country you are. In the case of capital crimes (killings, kidnapping, etc.), the investigation effort will always be greater than, for example, in the case of a simple fraud. Examinations cost time and, of course, money. And the effort always has to be in a reasonable relation to the original offense and the damage. This is actually the case all over the world (with simple to medium-level drug offenses not being considered as so serious in most European countries, whereas in the USA they are rated as very serious crimes).

The problem today is not so much the fingerprints but the genetic traces that you leave behind. Here it is sufficient, for example, if you scratch your nose with latex gloves and then touch something. A few cells from your body (contained in sweat, sebum, tears, nasal secretions, saliva, etc.) are sufficient to determine your genetic fingerprint.

And this is more serious than your real fingerprint!

/u/HeadJanitor Moderator · 2 votes · 1 week ago · Link

Porous surfaces like paper fibers absorb the oils and sweat. Latent print deposits soak into the paper, even after it has dried. Ammonia, baking soda, vinegar. None of these will work. Perhaps monochromatic laser, otherwise, no.

/u/somuchonmymind OP · 2 votes · 1 week ago · Link

Interesting, thank you.