I want to encrypt and decrypt one file using one password.
How can I use OpenSSL to do that?
I want to encrypt and decrypt one file using one password.
How can I use OpenSSL to do that?
 
    
     
    
    Security Warning: AES-256-CBC does not provide authenticated encryption and is vulnerable to padding oracle attacks. You should use something like age instead.
Encrypt:
openssl aes-256-cbc -a -salt -pbkdf2 -in secrets.txt -out secrets.txt.enc
Decrypt:
openssl aes-256-cbc -d -a -pbkdf2 -in secrets.txt.enc -out secrets.txt.new
 
    
     
    
    Though you have specifically asked about OpenSSL (see "Using OpenSSL" below for OpenSSL solution) you might want to consider using GPG instead for the purpose of encryption based on this article OpenSSL vs GPG for encrypting off-site backups?
To use GPG to do the same you would use the following commands:
To Encrypt:
gpg --output encrypted.data --symmetric --cipher-algo AES256 un_encrypted.data
To Decrypt:
gpg --output un_encrypted.data --decrypt encrypted.data
Note: You will be prompted for a password when encrypting or decrypt. And use --no-symkey-cache flag for no cache.
You likely want to use gpg instead of openssl as mentioned above but to answer the question using openssl:
To Encrypt:
openssl enc -aes-256-cbc -in un_encrypted.data -out encrypted.data
To Decrypt:
openssl enc -d -aes-256-cbc -in encrypted.data -out un_encrypted.data
Note: You will be prompted for a password when encrypting or decrypt.
Your best source of information for openssl enc would probably be: https://www.openssl.org/docs/man1.1.1/man1/enc.html
Command line:
openssl enc takes the following form:
openssl enc -ciphername [-in filename] [-out filename] [-pass arg]
[-e] [-d] [-a/-base64] [-A] [-k password] [-kfile filename] 
[-K key] [-iv IV] [-S salt] [-salt] [-nosalt] [-z] [-md] [-p] [-P] 
[-bufsize number] [-nopad] [-debug] [-none] [-engine id]
Explanation of most useful parameters with regards to your question:
-e
    Encrypt the input data: this is the default.
-d    
    Decrypt the input data.
-k <password>
    Only use this if you want to pass the password as an argument. 
    Usually you can leave this out and you will be prompted for a 
    password. The password is used to derive the actual key which 
    is used to encrypt your data. Using this parameter is typically
    not considered secure because your password appears in 
    plain-text on the command line and will likely be recorded in 
    bash history.
-kfile <filename>
    Read the password from the first line of <filename> instead of
    from the command line as above.
-a
    base64 process the data. This means that if encryption is taking 
    place the data is base64 encoded after encryption. If decryption 
    is set then the input data is base64 decoded before being 
    decrypted.
    You likely DON'T need to use this. This will likely increase the
    file size for non-text data. Only use this if you need to send 
    data in the form of text format via email etc.
-salt
    To use a salt (randomly generated) when encrypting. You always
    want to use a salt while encrypting. This parameter is actually
    redundant because a salt is used whether you use this or not 
    which is why it was not used in the "Short Answer" above!
-K key    
    The actual key to use: this must be represented as a string
    comprised only of hex digits. If only the key is specified, the
    IV must additionally be specified using the -iv option. When 
    both a key and a password are specified, the key given with the
    -K option will be used and the IV generated from the password 
    will be taken. It probably does not make much sense to specify 
    both key and password.
-iv IV
    The actual IV to use: this must be represented as a string 
    comprised only of hex digits. When only the key is specified 
    using the -K option, the IV must explicitly be defined. When a
    password is being specified using one of the other options, the 
    IV is generated from this password.
-md digest
    Use the specified digest to create the key from the passphrase.
    The default algorithm as of this writing is sha-256. But this 
    has changed over time. It was md5 in the past. So you might want
    to specify this parameter every time to alleviate problems when
    moving your encrypted data from one system to another or when
    updating openssl to a newer version.
 
    
    Encrypt:
openssl enc -in infile.txt -out encrypted.dat -e -aes256 -k symmetrickey
Decrypt:
openssl enc -in encrypted.dat -out outfile.txt -d -aes256 -k symmetrickey
For details, see the openssl(1) docs.
 
    
     
    
    DO NOT USE OPENSSL DEFAULT KEY DERIVATION.
Currently the accepted answer makes use of it and it's no longer recommended and secure.
It is very feasible for an attacker to simply brute force the key.
https://www.ietf.org/rfc/rfc2898.txt
PBKDF1 applies a hash function, which shall be MD2 [6], MD5 [19] or SHA-1 [18], to derive keys. The length of the derived key is bounded by the length of the hash function output, which is 16 octets for MD2 and MD5 and 20 octets for SHA-1. PBKDF1 is compatible with the key derivation process in PKCS #5 v1.5. PBKDF1 is recommended only for compatibility with existing applications since the keys it produces may not be large enough for some applications.
PBKDF2 applies a pseudorandom function (see Appendix B.1 for an example) to derive keys. The length of the derived key is essentially unbounded. (However, the maximum effective search space for the derived key may be limited by the structure of the underlying pseudorandom function. See Appendix B.1 for further discussion.) PBKDF2 is recommended for new applications.
Do this:
openssl enc -aes-256-cbc -pbkdf2 -iter 20000 -in hello -out hello.enc -k meow
openssl enc -d -aes-256-cbc -pbkdf2 -iter 20000 -in hello.enc -out hello.out
Note: Iterations in decryption have to be the same as iterations in encryption.
Iterations have to be a minimum of 10000. Here is a good answer on the number of iterations: https://security.stackexchange.com/a/3993
Also... we've got enough people here recommending GPG. Read the damn question.
 
    
    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 hashing (10,000 by default).
To encrypt a file:
openssl aes-256-cbc -e -salt -pbkdf2 -iter 10000 -in plaintextfilename -out encryptedfilename
To decrypt a file:
openssl aes-256-cbc -d -salt -pbkdf2 -iter 10000 -in encryptedfilename -out plaintextfilename
Note: An equivalent/compatible implementation in javascript (using the web crypto api) can be found at https://github.com/meixler/web-browser-based-file-encryption-decryption.
 
    
    Update using a random generated public key.
Encypt:
openssl enc -aes-256-cbc -a -salt -in {raw data} -out {encrypted data} -pass file:{random key}
Decrypt:
openssl enc -d -aes-256-cbc -in {ciphered data} -out {raw data}
To Encrypt:
$ openssl bf < arquivo.txt > arquivo.txt.bf
To Decrypt:
$ openssl bf -d < arquivo.txt.bf > arquivo.txt
bf === Blowfish in CBC mode
 
    
    There is an open source program that I find online it uses openssl to encrypt and decrypt files. It does this with a single password. The great thing about this open source script is that it deletes the original unencrypted file by shredding the file. But the dangerous thing about is once the original unencrypted file is gone you have to make sure you remember your password otherwise they be no other way to decrypt your file.
Here the link it is on github
https://github.com/EgbieAnderson1/linux_file_encryptor/blob/master/file_encrypt.py
 
    
    Note that the OpenSSL CLI uses a weak non-standard algorithm to convert the passphrase to a key, and installing GPG results in various files added to your home directory and a gpg-agent background process running. If you want maximum portability and control with existing tools, you can use PHP or Python to access the lower-level APIs and directly pass in a full AES Key and IV.
Example PHP invocation via Bash:
IV='c2FtcGxlLWFlcy1pdjEyMw=='
KEY='Twsn8eh2w2HbVCF5zKArlY+Mv5ZwVyaGlk5QkeoSlmc='
INPUT=123456789023456
ENCRYPTED=$(php -r "print(openssl_encrypt('$INPUT','aes-256-ctr',base64_decode('$KEY'),OPENSSL_ZERO_PADDING,base64_decode('$IV')));")
echo '$ENCRYPTED='$ENCRYPTED
DECRYPTED=$(php -r "print(openssl_decrypt('$ENCRYPTED','aes-256-ctr',base64_decode('$KEY'),OPENSSL_ZERO_PADDING,base64_decode('$IV')));")
echo '$DECRYPTED='$DECRYPTED
This outputs:
$ENCRYPTED=nzRi252dayEsGXZOTPXW
$DECRYPTED=123456789023456
You could also use PHP's openssl_pbkdf2 function to convert a passphrase to a key securely.
