PEM certificate public key padding

Asked Apr 23 '21 at 11:28

Active Apr 23 '21 at 12:08

Viewed 318 times

I have a x509 certificate (PEM format) and I want to load it in Go so that I can extract the public key and the signature from it. Extracting the signature works fine, but when extracting the public key I get some padding + the public key.

Does anyone know why that padding is added and how I can remove it?

For example:

the public key is : 04acad3942581b4b1992586....
when extracting it in Go i get: 3076301006072a8648ce3d020106052b81040022036200[then pe public key]

The code looks like this:

pub_key_str := cert.RawSubjectPublicKeyInfo
pub_key_hex := hex.EncodeToString(pub_key_str)

edited Apr 23 '21 at 12:08

kostix

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asked Apr 23 '21 at 11:28

Alexandra

Why do you access the `Raw*` field? What about the `PublicKey` field? – Eli Bendersky Apr 23 '21 at 13:09
Does https://stackoverflow.com/q/39410808/8206 help? – Eli Bendersky Apr 23 '21 at 13:10
I wanted to print the value of the public key in base64. i couldn't do it using the PublicKey field. – Alexandra Apr 24 '21 at 12:00
Printing its value depends on what kind of key it is. `ecdsa` keys have a "curve" in addition to bigint numbers (see `ecdsa.PublicKey`). `rsa.Key` has a bigint and an int. Each one is different. You can follow the technique outlined in the post in my comment and decide how to print each key. – Eli Bendersky Apr 24 '21 at 12:51
I will try it. Thank you. – Alexandra Apr 24 '21 at 15:45

PEM certificate public key padding

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