Mastering Blockchain - Second Edition

How to generate a digital signature using OpenSSL

The first step is to generate a hash of the message file:

$ openssl dgst -sha256 message.txt 
SHA256(message.txt)=
eb96d1f89812bf4967d9fb4ead128c3b787272b7be21dd2529278db1128d559c  

Both hash generation and signing can be done in a single step, as shown here. Note that privatekey.pem is generated in the steps provided previously:

$ openssl dgst -sha256 -sign privatekey.pem -out signature.bin message.txt  

Now, let's display the directory showing the relevant files:

$ ls -ltr total 36
-rw-rw-r-- 1 drequinox drequinox 14 Sep 21 05:54 message.txt
-rw-rw-r-- 1 drequinox drequinox 32 Sep 21 05:57 message.bin
-rw-rw-r-- 1 drequinox drequinox 45 Sep 21 06:00 message.b64
-rw-rw-r-- 1 drequinox drequinox ...