How to generate a new RSA key pair with a longer key size using OpenSSL "genpkey" command?

If you need a new RSA key pair with a longer key size for testing purpose, you can use the OpenSSL "genpkey" command as shown below:

C:\Users\fyicenter>time
The current time is: 18:43:27.27

C:\Users\fyicenter>\local\openssl\openssl
OpenSSL> genpkey -algorithm rsa -out rsa_test.key -pkeyopt rsa_keygen_bits:10240
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++
OpenSSL> exit

C:\Users\fyicenter>time
The current time is: 18:46:46.85

What this test tells us:

• OpenSSL allows you to generate longer RSA keys. But it will take a longer time. A 10240-bit RSA key pair took more than 3 minutes to generate on a laptop computer.

⇒ OpenSSL "genpkey -pkeyopt rsa_keygen_pubexp:3" - RSA Public Exponent

⇐ OpenSSL "genpkey rsa_keygen_bits:256" - RSA Short Keys

⇑ OpenSSL "genpkey" Command for RSA Keys

⇑⇑ OpenSSL Tutorials