While Encrypting a File with a Password from the Command Line using OpenSSL is very useful in its own right, the real power of the OpenSSL library is its ability to support the use of public key cryptograph for encrypting or validating data in an unattended manner (where the password is not required to encrypt) is done with public keys. The Commands to Run.
- Openssl Rsa Check Key
- Openssl Generate Rsa 256 Key Size
- Openssl Generate Rsa 256 Key Loader
- Openssl Generate Rsa Certificate
- Openssl Generate Rsa 256 Key Pair
< Cryptography
- The example below will generate a 2048 bit key file with a SHA-256 signature. Openssl genrsa -out keyname.key 2048 If you want extra security you could increase the bit lengths.
- This might be a noob question, but I couldn't find its answer anywhere online: why does an OpenSSL generated 256-bit AES key have 64 characters? The command I'm using to generate the key is: $ ope.
- Apr 28, 2012 Here we’re using the RSAgeneratekey function to generate an RSA public and private key which is stored in an RSA struct. The key length is the first parameter; in this case, a pretty secure 2048 bit key (don’t go lower than 1024, or 4096 for the paranoid), and the public exponent (again, not I’m not going into the math here), is the second parameter.
- Asymmetric key. Private key generation: openssl genrsa -out keyfile.key 4096 Public key generation from private key: openssl rsa -in keyfile.key -pubout -out keyfile.pub Now when I read OpenSSL help regarding rsa it says: The rsa command processes RSA keys. They can be converted between various forms and their components printed out.
Download and install the OpenSSL runtimes. If you are running Windows, grab the Cygwin package.
OpenSSL can generate several kinds of public/private keypairs.RSA is the most common kind of keypair generation.[1]
Other popular ways of generating RSA public key / private key pairs include PuTTYgen and ssh-keygen.[2][3]
Generate an RSA keypair with a 2048 bit private key[edit]
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'
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 types in the password to unlock the private key.Many of these people generate 'a private key with no password'.[7]Some of these people, instead, generate a private key with a password,and then somehow type in that password to 'unlock' the private key every time the server reboots so that automated toolscan make use of the password-protected keys.[8][3]
Further reading[edit]
- ↑Key Generation
- ↑Michael Stahnke.'Pro OpenSSH'.p. 247.
- ↑ ab'SourceForge.net Documentation: SSH Key Overview'
- ↑'genpkey(1) - Linux man page'
- ↑'Public – Private key encryption using OpenSSL'
- ↑'OpenSSL 1024 bit RSA Private Key Breakdown'
- ↑'DreamHost: Personal Backup'.
- ↑Troy Johnson.'Using Rsync and SSH: Keys, Validating, and Automation'.
- Internet_Technologies/SSH describes how to use 'ssh-keygen' and 'ssh-copy-id' on your local machine so you can quickly and securely ssh from your local machine to a remote host.
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This post briefly describes how to utilise AES to encrypt and decrypt files with OpenSSL.
AES - Advanced Encryption Standard (also known as Rijndael).
OpenSSL - Cryptography and SSL/TLS Toolkit
We’ll walk through the following steps:
![Key Key](/uploads/1/2/6/0/126087002/490303615.png)
- Generate an AES key plus Initialization vector (iv) with
openssl
and - how to encode/decode a file with the generated key/iv pair
Note: AES is a symmetric-key algorithm which means it uses the same key during encryption/decryption.
Generating key/iv pair
We want to generate a
256
-bit key and use Cipher Block Chaining (CBC).The basic command to use is
openssl enc
plus some options:-P
— Print out the salt, key and IV used, then exit-k <secret>
or-pass pass:<secret>
— to specify the password to use-aes-256-cbc
— the cipher name
Note: We decided to use no salt to keep the example simple.
Issue
openssl enc --help
for more details and options (e.g. other ciphernames, how to specify a salt, …).Encoding
Let's start with encoding
Hello, AES!
contained in the text file message.txt
:Openssl Rsa Check Key
Decoding
Openssl Generate Rsa 256 Key Size
Decoding is almost the same command line - just an additional
-d
for decrypting:Openssl Generate Rsa 256 Key Loader
Note: Beware of the line breaks
Openssl Generate Rsa Certificate
While working with AES encryption I encountered the situation where the encoder sometimes produces base 64 encoded data with or without line breaks...
Openssl Generate Rsa 256 Key Pair
Short answer: Yes, use the OpenSSL
-A
option.