36

I noticed that the string ICAgICAgICAgICAgICAg, in various repeating lengths, appears fairly often in public key certificates and ciphertexts.

What does this mean? Is it some kind of padding? Is it a quirk of the encryption?

  • 6
    Are you sure about the ciphertexts? It's actually impossible as the result of any usable encryption is a random-looking byte sequence. The probability of 15 consecutive spaces is 2**-120, i.e., practically zero. – maaartinus Dec 2 at 1:54
  • 16
    It means the certificate is made out of a polymer of Silver, Iodine and Carbon. The length of the chain depends on how long the certificate needs to be. – JDL Dec 2 at 17:14
55

ICAg represents three spaces when text is base64-encoded.

For example:

echo -n '      hello world' | openssl base64

produces:

ICAgICAgaGVsbG8gd29ybGQ=
  • 9
    Is there any particular reason why three spaces might be a common occurrence in public key certificates? – Délisson Junio Dec 1 at 20:40
  • 9
    Any long string of spaces would turn into n blocks of 3 spaces plus a maybe a final block of one or two spaces plus other characters – fernandopcg Dec 1 at 22:49
  • @DélissonJunio it should not be a common occurrence. There's no reason to add pointless blank space to a certificate, and in a ciphertext it's even more concerning. – Stop Harming Monica Dec 1 at 23:57
  • 13
    @StopHarmingMonica My guess is that the text before encoding had indentation using spaces. – Barmar Dec 2 at 8:36
  • 6
    @StopHarmingMonica Certificates do not contain any ciphertext. They often contain base-64 encoded text though. – Martin Bonner supports Monica Dec 2 at 11:21
31

The accepted answer doesn't show how to get the answer (it shows, how to verify it). Use

echo 'ICAgICAgICAgICAgICAg' | base64 -d

(producing a bunch of spaces) or

echo 'ICAgICAgICAgICAgICAg' | base64 -d | hexdump -C

producing

00000000  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20     |               |
0000000f

to see what's inside.

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