You use a key generator, and if not available, a random number generator to generate a key of the correct size, in this case 32 bytes. You can feed that to the cipher implementation. Then, if you need hexadecimals then you can convert or encode them explicitly to hexadecimals after. You have a certificate with a 4096 bit RSA key. There is no sense is going higher than that. Which symmetric encryption will be chosen by SSL depends only on what the server/client support, not on the key size of the certificate. You need to fix the server config, not the certificate. – CodesInChaos Feb 7 '14 at 17:41.

This page describes the command line tools for encryption and decryption. Enc is used for various block and stream ciphers using keys based on passwords or explicitly provided. It can also be used for Base64 encoding or decoding.

  • 4Examples
    • 4.2Encryption
  • My goal was to create a private key and to encrypt it with a strong cipher. That key would be used as a root certificate for an internal Certification Authority. However, eventhough openssl supports AES 128 GCM, I cannot generate and encrypt a key using this encryption algorithm.
  • This command uses AES 128 only to protect the RSA key pair with a passphrase, just in case an unauthorized person can get the key file. When your Apache server starts up, it must decrypt the key in memory to use it.
  • Oct 16, 2019  openssl aes-256-cbc -salt -a -d -in encrypted.txt -out plaintext.txt Asymmetric encryption. For Asymmetric encryption you must first generate your private key and extract the public key. Openssl genrsa -aes256 -out private.key 8912 openssl rsa -in private.key -pubout -out public.key To encrypt.
  • As mentioned in the other answers, previous versions of openssl used a weak key derivation function to derive an AES encryption key from the password. However, openssl v1.1.1 supports a stronger key derivation function, where the key is derived from the password using pbkdf2 with a randomly generated salt, and multiple iterations of sha256.

Synopsis[edit]

The basic usage is to specify a ciphername and various options describing the actual task.

You can obtain an incomplete help message by using an invalid option, eg. -help.

Cipher alogorithms[edit]

To get a list of available ciphers you can use the list-cipher-algorithms command

The output gives you a list of ciphers with its variations in key size and mode of operation. For example AES-256-CBC for AES with key size 256 bits in CBC-mode. Some ciphers also have short names, for example the one just mentioned is also known as aes256. These names are case insensitive. In addition none is a valid ciphername. This algorithms does nothing at all.

Options[edit]

The list of options is rather long.

-in filename
This specifies the input file.
-out filename
This specifies the output file. It will be created or overwritten if it already exists.
-e or -d
This specifies whether to encrypt (-e) or to decrypt (-d). Encryption is the default. Of course you have to get all the other options right in order for it to function properly. In particular it is necessary to give the correct cipher-name as well as -a, -A or -z options.
-a, -A, -base64
These flags tell OpenSSL to apply Base64-encoding before or after the cryptographic operation. The -a and -base64 are equivalent. If you want to decode a base64 file it is necessary to use the -d option. By default the encoded file has a line break every 64 characters. To suppress this you can use in addition to -base64 the -A flag. This will produce a file with no line breaks at all. You can use these flags just for encoding Base64 without any ciphers involved.
-bufsize n
Specify the buffer size. This concerns only internal buffers. It has nothing to do with the cryptographic algorithms in question.
-debug
Enable debugging output. This does not include any sensitive information. See also -P.
-engine id
Specify an engine for example to use special hardware.
-iv IV
This specifies the initialization vectorIV as hexadecimal number. If not explicitly given it will be derived from the password. See key derivation for details.
-k password, -kfile filename
Both option are used to specify a password or a file containing the password which is used for key derivation. However they are deprecated. You should use the -pass option instead. The equivalents are -pass pass:password and -pass file:filename respectively.
-K key
This option allows you to set the key used for encryption or decryption. This is the key directly used by the cipher algorithm. If no key is given OpenSSL will derive it from a password. This process is described in PKCS5#5 (RFC-2898).
-md messagedigest
This specifies the message digest which is used for key derivation. It can take one of the values md2, md5, sha or sha1.
-nopad
This disables standard padding.
-salt, -nosalt, -S salt
These options allow to switch salting on or off. With -Ssalt it is possible to explicitly give its value (in hexadecimal).
-p, -P
Additionally to any encryption tasks, this prints the key, initialization vector and salt value (if used). If -P is used just these values are printed, no encryption will take place.
-pass arg
This specifies the password source. Possible values for arg are pass:password or file:filename, where password is your password and filename file containing the password.
-z
Use this flag to enable zlib-compression. After a file is encrypted (and maybe base64 encoded) it will be compressed via zlib. Vice versa while decrypting, zlib will be applied first.

Examples[edit]

Base64 Encoding[edit]

To encode a file text.plain you can use

To decode a file the the decrypt option (-d) has to be used

Encryption[edit]

Basic Usage[edit]

The most basic way to encrypt a file is this

It will encrypt the file some.secret using the AES-cipher in CBC-mode. The result will be Base64 encoded and written to some.secret.enc. OpenSSL will ask for password which is used to derive a key as well the initialization vector.Since encryption is the default, it is not necessary to use the -e option.

Use a given Key[edit]

It also possible to specify the key directly. For most modes of operations (i.e. all non-ECB modes) it is then necessary to specify an initialization vector. Usually it is derived together with the key form a password. And as there is no password, also all salting options are obsolete.

The key and the IV are given in hex. Their length depending on the cipher and key size in question.

The key above is one of 16 weak DES keys. It should not be used in practice.

Retrieved from 'https://wiki.openssl.org/index.php?title=Enc&oldid=2894'

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:

  • 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

/call-of-duty-black-ops-4-key-generator-no-survey.html. Let's start with encoding Hello, AES! contained in the text file message.txt:

Decoding

Decoding is almost the same command line - just an additional -d for decrypting:

Note: Beware of the line breaks

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 Aes 256 Key Base64

Short answer: Yes, use the OpenSSL -A option.