openSSL: How to generate RSA private, public key pair

Syntax

openssl genrsa -des3 -out {FILE_NAME} {KEY_SIZE}

 

Example

openssl genrsa -des3 -out my_rsa_key_pair 2048

 Option -des3 make sure that the pem file generated in the above step will be protected by a passphrase.

 

$openssl genrsa -des3 -out my_rsa_key_pair 2048
Generating RSA private key, 2048 bit long modulus
..................................+++
..........................+++
e is 65537 (0x10001)
Enter pass phrase for my_rsa_key_pair:
Verifying - Enter pass phrase for my_rsa_key_pair:
$
$ls
my_rsa_key_pair

 

Export private key to a pem file

Export private key to privateKey.pem file by executing below commands. 

openssl pkcs8 -topk8 -inform PEM -in my_rsa_key_pair -outform PEM -out privateKey.pem -nocrypt

 

$openssl pkcs8 -topk8 -inform PEM -in my_rsa_key_pair -outform PEM -out privateKey.pem -nocrypt
Enter pass phrase for my_rsa_key_pair:
$
$ls
my_rsa_key_pair	privateKey.pem
$
$cat privateKey.pem 
-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----

 Export public key to a pem file

Export public key to publicKey.pem file by executing below command.

openssl rsa -in my_rsa_key_pair -outform PEM -pubout -out publicKey.pem

$openssl rsa -in my_rsa_key_pair -outform PEM -pubout -out publicKey.pem
Enter pass phrase for my_rsa_key_pair:
writing RSA key
$
$ls
my_rsa_key_pair	publicKey.pem
$
$cat publicKey.pem 
-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoIEO7wKib2IWL7+1ehnq
A0tufAXgDREoSlrJRqjfFekdsSzAf3Rcsg7edGARW+4EnJYmUJjYxQ46PxG7WhEx
scU7+fefEzgOFX7qxMB68zG8goU2cACpQSob8slRTdmQEy0dIzIPe4On9T3Q7wmB
SG5NeUTCo0l0hM+8RvCuoSr5HaBapODDkR77wtXuN/PiqsIcEoFQmuQ9BFENB5um
lDo0a1cJ+4rhv6ZLZ3T1jFn6nEvchlCHTpYNhda2UHaK3o9DvTAlbCBDjZxl4Urc
JxiTHIRnK2hbBLEvCUTplXGUFfvHmzzNkfoZiEItcQAMOLLVkOBCZCatm0h6KfXp
BwIDAQAB
-----END PUBLIC KEY-----

 

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