[openssl-users] Payload-checksum in PEM?

[Viktor Dukhovni]

> On Mar 8, 2018, at 11:25 AM, etc at coderhacks.com wrote:
> 
> # openssl cms -sign -in myfile.txt -md md5 -signer cer.txt -inkey key.txt -outform PEM > pem.txt
> 
> # md5sum myfile.txt
> 
> Can I expect to find the md5sum checksum somewhere in the ASN1 of pem.txt???
> 
> # openssl asn1parse -in pem.txt
> 
> As far I see it is not there - but maybe it is just a quick step to it?

When signing, the checksum is part of the signature, so you'd have to
decrypt the signature block with the signer's public key via:

	openssl rsautl -pubin -raw -encrypt -inkey pubkey.pem

and find the message digest there.

-- 
	Viktor.