OpenSSL: Generating an RSA Key From the Command Line

OpenSSL: Generating an

RSA Key From the

Command Line

 

Generate a 2048 bit RSA Key

openssl genrsa  -out private.pem 2048

Generate a 3072 bit RSA Key

openssl genrsa  -out private.pem 3072

Generate a 4096 bit RSA Key

openssl genrsa  -out private.pem 4096

prints out the various public or private key

components in plain text in addition to the

encoded version

openssl rsa -text -in private.pem

 

Export the RSA Public Key to a File

openssl rsa -in private.pem -outform PEM -pubout -out public.pem

   

The Generated Key Files

The generated files are base64-encoded encryption keys in plain text format.
If you select a password for your private key, its file will be encrypted with
your password. Be sure to remember this password or the key pair becomes
useless.

The private.pem file looks something like this:

-----BEGIN RSA PRIVATE KEY----- MIIEogIBAAKCAQEA6JtguftyimdvYIG4X7r6MmrPHBlhs9CrxPZ0nAb/a7bCDxav /GSEKVQfE6JBI1Ehc7D8ylpI607hTXuBTqVA4Q/nWKPThdeknIl3ORhFlHfHjBhD H60BwweOuV7mj0lT+gwdqUP/8HtcO6KkiKtXOZ7clZNPyD8kb/A5pq25ucMlcxhO /aDteFmSudaftwp5CYFfLyX+BIel3mBqQ95DdQmZROrtgDQuspU4kCfMflbyPYso JgB3uLV/RH7IWvUHwR+IAVjkjluBWdACOcOvEtcss/gI7UIJ2RgcAfO7zICPIk7B 4X49/dzmqDFjBMrm/DiSTbcBRoDHuEvtt59x1wIDAQABAoIBAFPRqclbEqtNGpVs KURV3FLOqlM10j85sqwHI34WB3SJJuTJCCGrFvTNm2U30sEnOya1YGKKpjwk8Is7 Nh1g70AquvL2FgLk8ix2XL/2PxyBDSculwGTFk9xKb0itXJsuhYgx493MYM28MWM lj2pgIUC+fnsW5ONLVQo/J1TfNmzCJXcQ3pBq428oljtc5HUEgd9WYr79nwCnb4I nsH8rJ7JisLrZEVX2sjO7V7JiMJJ/BoSx5XVTREo2ESTsOxpXnHAsbWYof6fTZ9V 4zPI80canzfYnl6Xkm9F8eH+zI5eJRwRh4MlZ7DLtRGh80i370EHTm8k8vKBB4oV p1/zigECgYEA/AqIFP89ItpwfhGZzNQm1OwJk8dT0zwB428OJanpGnrRqcGmHFtM /hKJ1L+iBPsejzJJ4GlF12QWmQTsXf7YQjQz10eO8/Eb98JnFTZRV2M6t4yg5J// N8BqAiq47tcSMaTQoF+m7Y2ow+EWeOZeMFfbRLEazU3AjjBDxw+wVysCgYEA7EKz VYARhGEd+sEKvLGMiBDQPRfN/RTpYf6D6DclN/FOYSfMXtaMpue+fP0FspJHqs4K zTGpmPnYugxzT01CHg8C5N0PD5TorxHSWdR8U1lu8oZ5lt5eCjeipClCnwcBlFxL GabRTLqSxX60LwhzC1ufCx0YBIqSgCzU+ElKOgUCgYANPLhc8fLSC8rwtBfxzAqm ECeInWVnqLUorsJ9c+kMPPsaAVOqFZl7lpmqlM37mPzH5IpAwQasA1O0ga+wWBwf jgJTAi0d3sHrR0iGsq2e+1UwIrCokUakNPTcXEYONTl9ZfyXD68CtvfwIbg+bUrx GwwnFW4k7jp4vUwx/j7ytQKBgBk8JpuDSluxY9pctCDjdfcylItx93aIvUTSQpST D06iX5TRA2s9z1gkeJwxCmLAbRc5Wr4AB/Vm+lck7UwTHHTJda2sTueDKDdK2ATw RTdB3i/ZXTNYHQNKXfzay1rhDLIkCYF75+8iHnspxWUgqekUqDAvs1kI1A0MvNKo QV1hAoGAGY4uqbcqVdrdCp/qe5NFWB+9gWVMq88TBppOXIPaM7MWOJR2mtH4e9Q4 sM1JLOfcCYjYeKVhED7woHmwtl4fy048+PHxGhPoN3ph7mmLd40w8dltFzT6DASe QhKHiKlMXlmBfz2Et9oOdnQIBXiDUCHUtekEL4iiGguxdlhsI3Q= -----END RSA PRIVATE KEY-----

 

The public key, public.pem, file looks like:

-----BEGIN PUBLIC KEY----- MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA6JtguftyimdvYIG4X7r6 MmrPHBlhs9CrxPZ0nAb/a7bCDxav/GSEKVQfE6JBI1Ehc7D8ylpI607hTXuBTqVA 4Q/nWKPThdeknIl3ORhFlHfHjBhDH60BwweOuV7mj0lT+gwdqUP/8HtcO6KkiKtX OZ7clZNPyD8kb/A5pq25ucMlcxhO/aDteFmSudaftwp5CYFfLyX+BIel3mBqQ95D dQmZROrtgDQuspU4kCfMflbyPYsoJgB3uLV/RH7IWvUHwR+IAVjkjluBWdACOcOv Etcss/gI7UIJ2RgcAfO7zICPIk7B4X49/dzmqDFjBMrm/DiSTbcBRoDHuEvtt59x 1wIDAQAB -----END PUBLIC KEY-----

Encrypt/Decrypt Using RSA Public/Private Key

Step:-1

Create Demo.txt

cat demo.txt

Hello This is Demo for Encrypt file

Step:-2

Encrypt Demo.txt File using RSA Public Key

openssl rsautl -encrypt -in demo.txt -pubin -inkey public.pem -out demo_encrypted.pem

Step:-3

Decrypt Demo.txt Encrypted file using RSA Private Key

openssl rsautl -encrypt -in demo.txt -pubin -inkey public.pem -out demo_encrypted.pem

Step:4

Check the Decrypted file its should be same as demo.txt

cat demo_descrypted.pem Hello This is Demo for Encrypt file