2/18/2022 Openssl Generate Pem Key Pair
$ openssl rsa -pubout -in privatekey.pem -out publickey.pem writing RSA key A new file is created, publickey.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.
How to generate keys in PEM formatusing the OpenSSL command line tools?
RSA keys
The JOSE standard recommends a minimum RSA key size of 2048 bits.
To generate a 2048-bit RSA private + public key pair for use in RSxxx and PSxxxsignatures:
Elliptic Curve keys
To generate an EC key pair the curve designation must be specified. Note thatJOSE ESxxx signatures require P-256, P-384 and P-521 curves (see theircorresponding OpenSSL identifiers below).
Elliptic Curve private + public key pair for use with ES256 signatures:
Elliptic Curve private + public key pair for use with ES384 signatures:
Elliptic Curve private + public key pair for use with ES512 signatures:
PEM key parsing in Java
The BouncyCastle library provides a simpleutility to parse PEM-encoded keys in Java, to use them for JWS or JWE later.
For Maven you should include the following BouncyCastle dependencies (where1.52 is the latest stable version as of May 2015):
Example parsing of an PEM-encoded EC key in Java:
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.
The Commands to RunGenerate 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
Openssl Generate Pem FileDo 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:
The next section shows a full example of what each key file should look like.
The Generated Key FilesUse Openssl To Generate Key Pair
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. Auto generated primary key sql. 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. Random key generation in cryptography. Download bitcoin generator v6 5 with key. 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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