Open SSL AES-256 Encryption / Decryption Command Line and Java Code using bouncycastle

 

• OpenSSL encrypted files begin with an 8-byte signature: the ASCII characters "Salted__".
• Files have an 8-byte signature, followed by an 8(?)-byte salt. Following the salt is the encrypted data.
• The salt and password are to be combined in a particular way, to derive the encryption key and initialization vector.
• No information about which encryption cipher was used is stored in the file. In order to decrypt the file, the cipher must be known by external means, or guessed. (Obviously, the same goes for the password.)

Above is old/ deprecated mechanism of OpenSSL to derive encryption key.  So, many a time -one can see following warning while running OpenSSL commands - 

*** WARNING : deprecated key derivation used.

Using -iter or -pbkdf2 would be better.

Also, note that default message digest for OpenSSL has been changed from md5 to sha-256. So, one may face problem to decrypt encrypted file generated from, not same version of OpenSSL

Also, Refer - https://stackoverflow.com/questions/8674018/pbkdf2-with-bouncycastle-in-java

Command Line 

• Encrypt 

openssl enc -aes-256-cbc -e -salt -in <Input_File> -out <Output_File> -k <password> -md md5

• Decrypt

openssl enc -aes-256-cbc -d -salt -in <Input_File> -out <Output_File> -k <password> -md md5

Refer - https://www.openssl.org/docs/manmaster/man1/openssl-enc.html

For Java Code, One will need following dependencies - 

       <dependencies>

<dependency>

<groupId>org.bouncycastle</groupId>

<artifactId>bcpkix-jdk15on</artifactId>

<version>1.56</version>

</dependency>

<dependency>

<groupId>org.bouncycastle</groupId>

<artifactId>bcprov-jdk15on</artifactId>

<version>1.56</version>

</dependency>

</dependencies>

For Full Encryption/ Decryption Java Source code, refer - https://github.com/dinesh028/engineering/blob/master/encrypt/src/main/java/com/ds/decrypt/Decrypt.java