OpenSSL is well known for its ability to generate certificates but it can also be used to generate random data. Generates 32 random bytes (256bits) in a base64 encoded output: openssl rand -base64 32 Plaintext. Generates 32 random characters (256bits): openssl rand 32. An AES-128 expects a key of 128 bit, 16 byte. To generate such a key, use OpenSSL as: openssl rand 16 myaes.key AES-256 expects a key of 256 bit, 32 byte. To generate such a key, use: openssl rand 32 myaes.key – ingenue Oct 12 '17 at 11:57. Looking for Java implementation for decrypting a message encrypted using openssl -aes-256-cbc -a -salt command? Hot Network Questions MTG - Does this do an infinite combo? Likewise, you have to call AESsetdecryptkey (.) to setup the AES Structure required to decrypt data using the OpenSSL API; OpenSSL and AES Encryption (Options) I found a couple of different APIs that can be used to perform AES Encryption using OpenSSL.

OpenSSL, C++ and AES Encryption (Just scratching the surface)

Cryptography is a fascinating subject that I would like to learn more about. While I may not make any contributions in cryptology in my career, I can certainly appreciate the mathematics, mathematicians and engineers who have helped make encryption more mainstream. As I'm interested in applying cryptography in the software I create I decidd to look at how I can operate OpenSSL.

As with my previous foray into the world of Bouncy Castle (a C# Cryptographic library) I have found the documentation surrounding OpenSSL to be inadequate. While I hope what I write here can be useful to someone investigating one facet OpenSSL I hope to come back here in the future to refresh my memory when working with AES in OpenSSL in the future.

OpenSSL is written by monkeys [peereboom.us]
Reddit Commentary: OpenSSL is written by monkeys [reddit.com/r/programming]
Comparison of TLS implementations [wikipedia.org]
Compare SSL Libraries [curl.haxx.se]
NaCL: Networking and Cryptographic Library [nacl.cr.yp.to]
OpenSSL in BB10 Cascades [supportforums.blackberry.com]
How to choose an AES encryption mode (CBC ECB CTR OCB CFB)? [stackoverflow.com]
Block cipher mode of operation [wikipedia.org]
AES Encryption -Key Generation with OpenSSL (Get Random Bytes for Key) [stackoverflow.com]
How to do encryption using AES in Openssl [stackoverflow.com]
AES CBC encrypt/decrypt only decrypts the first 16 bytes [stackoverflow.com]
Initialization Vector [wikipedia.org]
AES encryption/decryption demo program using OpenSSL EVP apis [saju.net.in]
OpenSSL using EVP vs. algorithm API for symmetric crypto [stackoverflow.com]
Some AES Ciphers are only available via EVP (like XTS) [mail-archive.com, openssl-users list]

I started my journey into OpenSSL with energy and optimism- I was going to learn how to work with the worlds most commonly used cryptographic library. I figured that mastering this library would help me make better, more secure software. Upon investigating the API documentation and trying out some sample code it quickly became apparent that OpenSSL has a steep learning curve. I wouldn't be getting anything productive done anytime soon.

After my initial taste of OpenSSL I decided to look at other cryptographic libraries. Was there anything else available? I found quite a few different libraries that have different levels of capability. At the end of the day I wanted to learn a crypto library that was cross platform, well used and secure so I ended up where I started with OpenSSL. That's not to say that the other libraries are 'bad', I just found that for my goals the other libraries either had too many dependencies, didn't work on all the platforms I thought I would be working on or were too limited in functionality for my needs. If you are starting a crypto project that fits into a smaller box, the other options (Like NaCL or GnuTLS) may do what you need them to do.

In your .pro file, add this line:

LIBS += -lcrypto

Without it you won't be able to successfully build an application that leverages OpenSSL

When working with the AES_* APIs (such as AES_cbc_encrypt), be sure to pass in a copy of your Initialization Vector (IV) if you plan on using it elsewhere in your program. I found during my testing that if you only have one copy of the IV and use it in multiple locations that it 'gets corrupted' (for lack of a better term). This will be most visible when setting up a test method that Encrypts a string then immediately Decrypts it (as seen below).
Before using the AES API to encrypt, you have to run AES_set_encrypt_key(..) to setup the AES Structure required by the OpenSSL API. Likewise, you have to call AES_set_decrypt_key(..) to setup the AES Structure required to decrypt data using the OpenSSL API

I found a couple of different APIs that can be used to perform AES Encryption using OpenSSL. That's not to say that there may not be more, just that these are the ones I was able to find by googling:

AES API

This API lets you get right into encrypting or decrypting data using the AES cipher. The available functions can be found in openssl/aes.h
(At the time of this writing I was unable to find even a stub of a page on the OpenSSL Site that describes the AES API to any depth)

This API lets you abstract the specific type of encryption used. It makes it easy to change out which cryptographic provider is used with less refactoring on your part. The available function list can be found in openssl/evp.h

For my purposes I decided to use the AES API directly. I made this decision based on the fact that I seemed to get further faster with the examples that used the AES API. As I gain proficiency with OpenSSL I'll be able to come back later and (hopefully) swallow the EVP API if I need to.

In order to get the AES API to work with the ASCII data that I will be feeding it, I needed to setup:

A random number that can be used as an Encryption Key
A random number that can be used as an Initialization Vector
A couple of OpenSSL AES_KEY structures for encrypting and decrypting via the API
A function to pad my text input so it encrypts and decrypts cleanly

The result is this sample code which encrypts a string then decrypts it (minus error handling):

I look forward to getting more proficient with the OpenSSL Library. I bet I'll get the hang of it with a bit more practice.

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

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

Openssl Generate Aes 256 Key