x509v3-sign-rsa, x509v3-ssh-rsa and x509v3-rsa2048-sha256

murugesh pitchaiah murugesh.pitchaiah at gmail.com
Thu Sep 2 05:19:10 UTC 2021

Thanks for the response Dirk.

I tried, but could not see the certificate public key algorithm - as
x509v3-ssh-rsa or x509v3-rsa2048-sha256.

I use below openssl commands to generate the user certificate:

    openssl req -nodes -new -x509 -keyout  userkey.pem -out
userreq.pem -days 365 -config openssl.cnf

    openssl x509 -x509toreq -in userreq.pem -signkey userkey.pem -out tmp.pem

    openssl ca -config openssl.cnf -extensions  usr_cert -out
usercert.pem -infiles tmp.pem

I tried varying the bits size (1024/2048/4096)  and default_md
(sha1/sha256/sha512) in the openssl.cnf file.

Could anyone please share the steps to generate user certificates of
type: x509v3-ssh-rsa  and x509v3-rsa2048-sha256 ?

Thanks & Regards,
Murugesh P.

On 8/24/21, Dirk-Willem van Gulik <dirkx at webweaving.org> wrote:
> On 24 Aug 2021, at 09:47, murugesh pitchaiah <murugesh.pitchaiah at gmail.com>
> wrote:
>> Hi,
>> I am working on generating the x509v3 certificates for ssh user. I see
>> with the default_md as 'sha256', in openssl.cnf file, the
>> key/certificate is generated with algorithm type as 'x509v3-sign-rsa'.
>> I see its signature algorithm is :
>>    Signature Algorithm: sha256WithRSAEncryption
>>            Public Key Algorithm: rsaEncryption
>>                Public-Key: (2048 bit)
>> Can any one please share how to generate certificate for
>> x509v3-ssh-rsa and x509v3-rsa2048-sha256 ? Basically looking for
>> difference between these three type of public key algorithms ,and how
>> to generate certificate of these types:
>> x509v3-sign-rsa, x509v3-ssh-rsa and x509v3-rsa2048-sha256
>> Because, even for x509v3-sign-rsa - I see the size is 2048 bit and it
>> is sha256. Is it something to vary in 'default_md' (or newkey rsa:size
>> and -sha) fields to vary to generate these different cert types ?
> Try something like
> 	openssl req -new -x509 -newkey rsa:1024 -sha256 -keyout /dev/stdout -nodes
> -subj /CN=foo  |\
> 		openssl x509 -pubkey -noout | openssl rsa  -text -pubin -noout
> 	openssl req -new -x509 -newkey rsa:1024 -sha256 -keyout /dev/stdout -nodes
> -subj /CN=foo |\
>  			openssl x509 -text -noout | grep Signature
> And vary the newkey argument to see what it actually generates as an RSA
> key.
> In this example a 1024 bit one. You can also vary sha256 to things like md5,
> etc.
> Dw.

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