Transwiki:Generate a keypair using OpenSSL

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Download and install the OpenSSL runtimes. If you are running Windows, grab the Cygwin package.

[edit] Generate a 1024 bit RSA private key

Execute command: “openssl genrsa -out private_key.pem 1024”

e.g.

$ openssl genrsa -out private_key.pem 1024
Generating RSA private key, 1024 bit long modulus
.............................++++++
................................................................++++++
e is 65537 (0x10001)

[edit] Generating a public key from a private key

Execute command: "openssl rsa -pubout -in private_key.pem -out public_key.pem"

e.g.

$ openssl rsa -pubout -in private_key.pem -out public_key.pem
writing RSA key

A new file is created, public_key.pem, with the public key.

[edit] Viewing the key elements

Execute command: "openssl rsa -text -in private_key.pem"

All parts of private_key.pem are printed to the screen. This includes the modulus (also referred to as public key and n), public exponent (also referred to as e and exponent; default value is 0x010001), private exponent, and primes used to create keys (prime1, also called p, and prime2, also called q), as well as a few other variables used to perform RSA operations faster and the Base64 PEM encoded version of the key.