How to use OpenSSL to encrypt decrypt files

Question

I want to encrypt and decrypt one file using one password  How can I use OpenSSL to do that

User · Answer

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.

User · Answer

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 -in secrets txt -out secrets txt enc  Decrypt  openssl aes-256-cbc -d -a -in secrets txt enc -out secrets txt new  More details on the various flags

User · Answer

To Encrypt     openssl bf  lt  arquivo txt  gt  arquivo txt bf   To Decrypt     openssl bf -d  lt  arquivo txt bf  gt  arquivo txt   bf     Blowfish in CBC mode

User · Answer

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

User · Answer

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

User · Answer

Short Answer   You likely want to use gpg instead of openssl so see  Additional Notes  at the end of this answer  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     Long Answer   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  lt password gt      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  lt filename gt      Read the password from the first line of  lt filename gt  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      Additional Notes   Though you have specifically asked about OpenSSL 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

User · Answer

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

User · Answer

Additional comments to mti2935 good answer   It seems the higher iteration the better protection against brute force  and you should use a high iteration as you can afford performance resource wise    On my my old Intel i3-7100 encrypting a rather big file 1 5GB    time openssl enc -aes256 -e -pbkdf2 -iter 10000 -pass pass  mypassword  -in  InputFile  -out  OutputFile   Seconds  2 564s   time openssl enc -aes256 -e -pbkdf2 -iter 262144 -pass pass  mypassword  -in  InputFile  -out  OutputFile   Seconds   2 775s   Not really any difference  didn t check memory usage though     With today s GPUs  and even faster tomorrows  I guess billion brute-force iteration seems possible every seconds   12 years ago a NVIDIA GeForce 8800 Ultra could iterate over 200 000 millions sec iterations  MD5 hashing though    source  Ainane-Barrett-Johnson-Vivar-OpenSSL pdf

User · Answer

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

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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

[encryption] How to use OpenSSL to encrypt/decrypt files?

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