While Encrypting a File with a Password from the Command Line using OpenSSLis very useful in its own right, the real power of the OpenSSL library is itsability to support the use of public key cryptograph for encrypting orvalidating data in an unattended manner (where the password is not required toencrypt) is done with public keys.

Generate Public Private Key Openssl
Generate Public And Private Key Using Openssl
Openssl Generate Private Key Csr
Generate Public Private Key

Mar 30, 2015 1. Type the following command in an open terminal window on your computer to generate your private key using SSL: $ openssl genrsa -out /path/to/wwwservercom.key 2048. This will invoke OpenSSL, instruct it to generate an RSA private key using the DES3 cipher, and send it as an output to a file in the same directory where you ran the command. Hit Enter to generate your private key.
I would like to create an EC private an public key and have them in one file. I can create a private key with: openssl ecparam -genkey -name prime256v1 -noout -out ec256-key-pair.pem But like th.

You can generate a public-private keypair with the genrsa context (the last number is the keylength in bits): openssl genrsa -out keypair.pem 2048 To extract the public part, use the rsa context: openssl rsa -in keypair.pem -pubout -out publickey.crt Finally, convert the original keypair to PKCS#8 format with the pkcs8 context. Public Key Cryptography, or Asymmetric Cryptography, is a cryptographic system that uses pairs of keys: Public Key and Private Key. It is one of the most important (if not the most important) part of cryptocurrency protocols, and it is used in sev.

The Commands to Run

Generate a 2048 bit RSA Key

You can generate a public and private RSA key pair like this:

openssl genrsa -des3 -out private.pem 2048

That generates a 2048-bit RSA key pair, encrypts them with a password you provideand writes them to a file. You need to next extract the public key file. You willuse this, for instance, on your web server to encrypt content so that it canonly be read with the private key.

Export the RSA Public Key to a File

This is a command that is

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

The -pubout flag is really important. Be sure to include it.

Next open the public.pem and ensure that it starts with-----BEGIN PUBLIC KEY-----. This is how you know that this file is thepublic key of the pair and not a private key.

To check the file from the command line you can use the less command, like this:

less public.pem

Do Not Run This, it Exports the Private Key

A previous version of the post gave this example in error.

openssl rsa -in private.pem -out private_unencrypted.pem -outform PEM

The error is that the -pubout was dropped from the end of the command.That changes the meaning of the command from that of exporting the public keyto exporting the private key outside of its encrypted wrapper. Inspecting theoutput file, in this case private_unencrypted.pem clearly shows that the keyis a RSA private key as it starts with -----BEGIN RSA PRIVATE KEY-----.

Visually Inspect Your Key Files

It is important to visually inspect you private and public key files to makesure that they are what you expect. OpenSSL will clearly explain the nature ofthe key block with a -----BEGIN RSA PRIVATE KEY----- or -----BEGIN PUBLIC KEY-----.

You can use less to inspect each of your two files in turn:

less private.pem to verify that it starts with a -----BEGIN RSA PRIVATE KEY-----
less public.pem to verify that it starts with a -----BEGIN PUBLIC KEY-----

The next section shows a full example of what each key file should look like.

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 withyour password. Be sure to remember this password or the key pair becomes useless.

The private.pem file looks something like this:

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

Protecting Your Keys

Depending on the nature of the information you will protect, it’s important tokeep the private key backed up and secret. The public key can be distributedanywhere or embedded in your web application scripts, such as in your PHP,Ruby, or other scripts. Again, backup your keys!

Remember, if the key goes away the data encrypted to it is gone. Keeping aprinted copy of the key material in a sealed envelope in a bank safety depositbox is a good way to protect important keys against loss due to fire or harddrive failure.

Oh, and one last thing.

If you, dear reader, were planning any funny business with the private key that I have just published here. Know that they were made especially for this series of blog posts. I do not use them for anything else.

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Generate an RSA keypair with a 2048 bit private key[edit]

Generate Public Private Key Openssl

Execute command: 'openssl genpkey -algorithm RSA -out private_key.pem -pkeyopt rsa_keygen_bits:2048'^[4] (previously “openssl genrsa -out private_key.pem 2048”)

e.g.

Make sure to prevent other users from reading your key by executing chmod go-r private_key.pem afterward.

Extracting the public key from an RSA keypair[edit]

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

Generate Public And Private Key Using Openssl

e.g.

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

It is relatively easy to do some cryptographic calculations to calculate the public key from the prime1 and prime2 values in the public key file.However, OpenSSL has already pre-calculated the public key and stored it in the private key file.So this command doesn't actually do any cryptographic calculation -- it merely copies the public key bytes out of the file and writes the Base64 PEM encoded version of those bytes into the output public key file.^[5]

Viewing the key elements[edit]

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), a few other variables used to perform RSA operations faster, and the Base64 PEM encoded version of all that data.^[6](The Base64 PEM encoded version of all that data is identical to the private_key.pem file).

Password-less login[edit]

Often a person will set up an automated backup process that periodically backs up all the content on one 'working' computer onto some other 'backup' computer.

Because that person wants this process to run every night, even if no human is anywhere near either one of these computers, using a 'password-protected' private key won't work -- that person wants the backup to proceed right away, not wait until some human walks by and