What does this "ICAgICAg…" mean in public key certificates and messages?

Question

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?

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 02 '19 at 01:54
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 02 '19 at 17:14

score 57 · Accepted Answer · answered Dec 01 '19 at 02:38

57

ICAg represents three spaces when text is base64-encoded.

For example:

echo -n '      hello world' | openssl base64

produces:

ICAgICAgaGVsbG8gd29ybGQ=

answered Dec 01 '19 at 02:38

mti2935

9

Is there any particular reason why three spaces might be a common occurrence in public key certificates? – Délisson Junio Dec 01 '19 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 01 '19 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. – OrangeDog Dec 01 '19 at 23:57
14

@StopHarmingMonica My guess is that the text before encoding had indentation using spaces. – Barmar Dec 02 '19 at 08:36
7

@StopHarmingMonica Certificates do not contain any ciphertext. They often contain base-64 encoded text though. – Martin Bonner supports Monica Dec 02 '19 at 11:21
@MartinBonnersupportsMonica I know... "appears fairly often in public key certificates and ciphertexts" – OrangeDog Dec 02 '19 at 11:48

score 31 · Answer 2 · answered Dec 01 '19 at 17:31

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.

2 Answers2