Openssl genrsa -out rsa.private 1024 4. The private key is generated and saved in a file named 'rsa.private' located in the same folder.
For symmetic encryption, you can use the following:
To encrypt:
To decrypt:
For Asymmetric encryption you must first generate your private key and extract the public key.
To encrypt:
To decrypt:
You can't directly encrypt a large file using rsautl
. Instead, do the following:
openssl rand
, e.g. openssl rand 32 -out keyfile
.openssl rsautl
.openssl enc
, using the generated key from step 1.Ultimate solution for safe and high secured encode anyone file in OpenSSL and command-line:
Private key generation (encrypted private key):
With unecrypted private key:
With encrypted private key:
With existing encrypted (unecrypted) private key:
Encrypt binary file:
Encrypt text file:
What is what:
smime
— ssl command for S/MIME utility (smime(1)).-encrypt
— chosen method for file process.-binary
— use safe file process. Normally the input message is converted to 'canonical' format as required by the S/MIME specification, this switch disable it. It is necessary for all binary files (like a images, sounds, ZIP archives).-aes-256-cbc
— chosen cipher AES in 256 bit for encryption (strong). If not specified 40 bit RC2 is used (very weak). (Supported ciphers).-in plainfile.zip
— input file name.-out encrypted.zip.enc
— output file name.-outform DER
— encode output file as binary. If is not specified, file is encoded by base64 and file size will be increased by 30%.yourSslCertificate.pem
— file name of your certificate's. That should be in PEM format.That command can very effectively a strongly encrypt any file regardless of its size or format.
Decrypt binary file:
For text files:
What is what:
-inform DER
— same as -outform
above.-inkey private.key
— file name of your private key. That should be in PEM format and can be encrypted by password.-passin pass:your_password
— (optional) your password for private key encrypt.Creating a signed digest of a file:
Verify a signed digest:
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.
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.
This is a command that is
openssl rsa -in private.pem -outform PEM -pubout -out public.pem
Cd-key generator left 4 dead.
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
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. Command to generate ssh key in git bash. 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-----
.
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 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.
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.
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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