Openssl Generate Random Aes Key
AES-256 requires a 256-bit key, period. However there are different ways of building that 256-bit key. One way is to generate 256 random bits and take them as the key. You need to store these 256 bits somewhere, or you won't be able to decrypt what you've encrypted. May 07, 2019 Make a backup of the original key. Linux/Mac: cp myCA.key myCA.key.withpwd Windows: copy myCA.key myCA.key.withpwd. Export the CA key without a password. This is useful so you don't have to keep track of the password and/or use a script to sign self-signed SSL certificates. Openssl rsa -in myCA.key.withpwd -out myCA.key. This a snippet to generate a psuedo random password fast via the command line with OpenSSL. It generates a number of random bytes, which can either be output raw, as Base64 or as HEX. The Base64 output is a good password most of the time. If you like this article, consider sponsoring me by trying out a Digital Ocean VPS. Use the OpenSSL command-line tool, which is included with the Master Data Engine, to generate AES 128-, 192-, or 256-bit keys. The madpwd3 utility is used to create the password.
OpenSSL provides two command line tools for working with keys suitable for Elliptic Curve (EC) algorithms:
The only Elliptic Curve algorithms that OpenSSL currently supports are Elliptic Curve Diffie Hellman (ECDH) for key agreement and Elliptic Curve Digital Signature Algorithm (ECDSA) for signing/verifying.
Rsa key generation algorithm in java. x25519, ed25519 and ed448 aren't standard EC curves so you can't use ecparams or ec subcommands to work with them. If you need to generate x25519 or ed25519 keys then see the genpkey subcommand.
EC Private Key File Formats[edit]
By default OpenSSL will work with PEM files for storing EC private keys. These are text files containing base-64 encoded data. A typical traditional format private key file in PEM format will look something like the following, in a file with a '.pem' extension:
Or, in an encrypted form like this:
You may also encounter PKCS8 format private keys in PEM files. These look like this:
Or, in an encrypted form like this:
PKCS8 private key files, like the above, are capable of holding many different types of private key - not just EC keys.
You can convert between these formats if you like. All of the conversion commands can read either the encrypted or unencrypted forms of the files however you must specify whether you want the output to be encrypted or not. To convert a PKCS8 file to a traditional encrypted EC format use:
You can replace the first argument 'aes-128-cbc' with any other valid openssl cipher name (see Manual:enc(1) for a list of valid cipher names). To convert a PKCS8 file to a traditional unencrypted EC format, just drop the first argument:
Or to convert from a traditional EC format to an encrypted PKCS8 format use:
Or to a non-encrypted PKCS8 format use:
Note that by default in the above traditional format EC Private Key files are not encrypted (you have to explicitly state that the file should be encrypted, and what cipher to use), whilst for PKCS8 files the opposite is true. The default is to encrypt - you have to explicitly state that you do not want encryption applied if appropriate using the '-nocrypt' option.
As well as PEM format all of the above types of key file can also be stored in DER format. This is a binary format and so is not directly human readable - unlike a PEM file. A PEM file is essentially just DER data encoded using base 64 encoding rules with a header and footer added. Often it is more convenient to work with PEM files for this reason.
The openssl commands typically have options '-inform DER' or '-outform DER' to specify that the input or output file is DER respectively. So for example the command to convert a PKCS8 file to a traditional encrypted EC format in DER is the same as above, but with the addition of '-outform DER':
Note that you cannot encrypt a traditional format EC Private Key in DER format (and in fact if you attempt to do so the argument is silently ignored!). The same is not true for PKCS8 files - these can still be encrypted even in DER format. So for example the following will convert a traditional format key file to an ecrypted PKCS8 format DER encoded key:
EC Public Key File Formats[edit]
EC Public Keys are also stored in PEM files. A typical EC public key looks as follows:
This format is used to store all types of public keys in OpenSSL not just EC keys.
It is possible to create a public key file from a private key file (although obviously not the other way around!):
As above a DER encoded version can be created using '-outform DER':
Generating EC Keys and Parameters[edit]
An EC Parameters file contains all of the information necessary to define an Elliptic Curve that can then be used for cryptographic operations (for OpenSSL this means ECDH and ECDSA). OpenSSL contains a large set of pre-defined curves that can be used. The full list of built-in curves can be obtained through the following command:
An EC parameters file can then be generated for any of the built-in named curves as follows:
Replace secp256k1 in the above with whichever curve you are interested in.
Keys can be generated from the ecparam command, either through a pre-existing parameters file or directly by selecting the name of the curve. To generate a private/public key pair from a pre-eixsting parameters file use the following:
Or to do the equivalent operation without a parameters file use the following:
Information on the parameters that have been used to generate the key are embedded in the key file itself.
By default, when creating a parameters file, or generating a key, openssl will only store the name of the curve in the generated parameters or key file, not the full set of explicit parameters associated with that name. For example:
This will simply confirm the name of the curve in the parameters file by printing out the following:
If you wish to examine the specific details of the parameters associated with a particular named curve then this can be achieved as follows:
The above command shows the details for a built-in named curve from a file, but this can also be done directly using the '-name' argument instead of '-in'. The output will look similar to the following:
The meaning of each of these parameters is discussed further on this page.
Parameters and key files can be generated to include the full explicit parameters instead of just the name of the curve if desired. This might be important if, for example, not all the target systems know the details of the named curve. In OpenSSL version 1.0.2 new named curves have been added such as brainpool512t1. Attempting to use a parameters file or key file in versions of OpenSSL less than 1.0.2 with this curve will result in an error:
This problem can be avoided if explicit parameters are used instead. So under OpenSSL 1.0.2 you could create a parameters file like this:
Looking at the parameters file you will notice that it is now much longer:
The full parameters are included rather than just the name. This can now be processed by versions of OpenSSL less than 1.0.2. So under 1.0.1:
This will correctly display the parameters, even though this version of OpenSSL does not know about this curve.
The same is true of key files. So to generate a key with explicit parameters:
This key file can now be processed by versions of openssl that do not know about the brainpool curve.
It should be noted however that once the parameters have been converted from the curve name format into explicit parameters it is not possible to change them back again, i.e. there is no utility to take a set of explicit parameters and work out which named curve they are associated with.
See also[edit]
Symmetic encryption
For symmetic encryption, you can use the following:
To encrypt:
To decrypt:
Asymmetric encryption
For Asymmetric encryption you must first generate your private key and extract the public key.
To encrypt:
To decrypt:
Encripting files
You can't directly encrypt a large file using rsautl. Instead, do the following:
- Generate a key using
openssl rand, e.g.openssl rand 32 -out keyfile. - Encrypt the key file using
openssl rsautl. - Encrypt the data using
openssl enc, using the generated key from step 1. - Package the encrypted key file with the encrypted data. The recipient will need to decrypt the key with their private key, then decrypt the data with the resulting key.
Generate Aes Key Openssl
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 a file
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 a file
Decrypt binary file:
For text files:
What is what:
-inform DER— same as-outformabove.-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.
Verification
Creating a signed digest of a file:
Openssl Generate Private Key
Verify a signed digest: