Bonjour,
Without knowing what functions you’re calling when you try to encrypt data
using the key Key3_wo16, I can only guess. And I’m guessing that you’re calling
a function that expects to find a public key encoded in a SubjectPublicKeyInfo
structure, and since this Key3_wo16 object is not such a structure, the
function fails.
What you can do is :
* Take your public keys (for example Key2_w16)
* Check that the first 16 bytes are what you expect to have
* Pass the remainder of the file to the d2i_RSAPublicKey() function
* Use the resulting RSA public key the way you want
Cordialement,
Erwann Abalea
De : prithiraj das
Date : lundi 17 décembre 2018 à 08:23
À : Erwann Abalea , "openssl-users@openssl.org"
Objet : Re: [openssl-users] RSA Public Key error
Hi Erwann/All,
Thank you for your earlier response. I have done a couple of tests on the
originally generated 2048-bit RSA public key (let's say Key1_org) and the key
file containing 16 byte custom information after removing 24 bytes from the
originally generated key file and prepending those 16 bytes (let's say
Key2_w16). For my experiment(s), I also removed those 16 bytes from the key
Key2_w16 (which contains custom information) and the rest of the bytes were
written into a file. Lets name this keyfile Key3_wo16. I believe the presence
of custom 16 byte information resulted in asn1parse encoding/decoding errors as
mentioned in the previous mail..
So now, Key3_wo16 = Key2_w16 - the first 16 bytes = Key1_org - the first
24 bytes. And I performed asn1parse on Key3_wo16. The output of asn1parse on
this key is shown in the image file asn1parse of 24 byte removed.jpg which is
attached in the mail. And I also performed 2 asn1parse strparse opertions on
the originally generated public key Key1_org with strparse offsets 19 and 24. I
have attached screenshots of the same with names asn1parse strparse 19.jpg and
asn1parse strparse 24.jpg respectively. The outputs in all cases are the same.
In the screenshots, the (removed/blurred) respective INTEGER values in all
screenshots are the same.
What I want to know is why is OpenSSL throwing an error when try to encrypt
data using the key Key3_wo16? The same command used for encryption works when
the key Key1_org is used. I believe the INTEGER values contain the modulus and
exponent information and so, I was expecting the encryption to be successful
but OpenSSL fails to accept this key.
Can anyone please tell me what is going wrong here? Apart from the solution
suggested by Erwann , can anyone please suggest an alternative solution as we
need to work with the Key2_w16 ( the key containing the custom 16 byte
information after removing the originally present first 24 bytes)? That is the
only keyfile received by us.
Thanks and Regards,
Prithiraj
On Wed, 12 Dec 2018 at 12:32, Erwann Abalea via openssl-users
mailto:openssl-users@openssl.org>> wrote:
Bonjour,
Assuming the first 24 bytes you’re talking about are the very beginning of the
SPKI structure (that is, the enclosing SEQUENCE, and the AlgorithmIdentifier),
that means you’ve replaced up to the first byte of the BITSTRING containing the
public key (this byte indicates the number of unused bits) for a 2048bits RSA
key with 16 custom bytes.
That’s perfectly normal for OpenSSL to refuse to load that beast, and for
asn1parse to return errors (the first bytes do not represent a correct DER
encoding of anything).
Think of it as « I took a Jpeg file, replaced some bytes at the beginning by my
own, and now I can’t open the file again ». Those bytes are there for a reason.
A quick solution would be to *add* your 16 bytes before the public key, and
remove them when passing the rest of the bytes to OpenSSL.
Cordialement,
Erwann Abalea
De : openssl-users
mailto:openssl-users-boun...@openssl.org>>
au nom de prithiraj das
mailto:prithiraj@gmail.com>>
Répondre à : "openssl-users@openssl.org<mailto:openssl-users@openssl.org>"
mailto:openssl-users@openssl.org>>
Date : mercredi 12 décembre 2018 à 08:08
À : "openssl-users@openssl.org<mailto:openssl-users@openssl.org>"
mailto:openssl-users@openssl.org>>
Objet : [openssl-users] RSA Public Key error
Hi,
I have a RSA public key(PKCS 1v1.5) that I have obtained from somewhere. That
key has been obtained after removing the first 24 bytes from the originally
generated RSA public key. Those 24 bytes are being replaced by some custom 16
byte information which is being used as some sort of identifier in some future
task and those 16 bytes are playing no role in encryption. OpenSSL fails to
read this key. asn1parse shows some parsing error and most importantly RSA
encryption in OpenSSL using this key fails. The untampered version of the RSA
public key generated from the same source and containing the original 24 bytes
at the beginning of the key is successfully read by OpenSSL and t
