NAME
    enc - symmetric cipher routines

SYNOPSIS
    openssl enc -ciphername [-in filename] [-out filename] [-pass arg] [-e]
    [-d] [-a] [-A] [-k password] [-kfile filename] [-K key] [-iv IV] [-p]
    [-P] [-bufsize number] [-nopad] [-debug]

DESCRIPTION
    The symmetric cipher commands allow data to be encrypted or decrypted
    using various block and stream ciphers using keys based on passwords or
    explicitly provided. Base64 encoding or decoding can also be performed
    either by itself or in addition to the encryption or decryption.

OPTIONS
    -in filename
   the input filename, standard input by default.

    -out filename
   the output filename, standard output by default.

    -pass arg
   the password source. For more information about the format of arg
   see the PASS PHRASE ARGUMENTS section in openssl(1).

    -salt
   use a salt in the key derivation routines. This option should
   ALWAYS be used unless compatibility with previous versions of
   OpenSSL or SSLeay is required. This option is only present on
   OpenSSL versions 0.9.5 or above.

    -nosalt
   don't use a salt in the key derivation routines. This is the
   default for compatibility with previous versions of OpenSSL and
   SSLeay.

    -e encrypt the input data: this is the default.

    -d decrypt the input data.

    -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.

    -A if the -a option is set then base64 process the data on one line.

    -k password
   the password to derive the key from. This is for compatibility with
   previous versions of OpenSSL. Superseded by the -pass argument.

    -kfile filename
   read the password to derive the key from the first line of file-
   name. This is for computability with previous versions of OpenSSL.
   Superseded by the -pass argument.

    -S salt
   the actual salt to use: this must be represented as a string com-
   prised only of hex digits.

    -K key
   the actual key to use: this must be represented as a string com-
   prised only of hex digits. If only the key is specified, the IV
   must additionally 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 com-
   prised 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.

    -p print out the key and IV used.

    -P print out the key and IV used then immediately exit: don't do any
   encryption or decryption.

    -bufsize number
   set the buffer size for I/O

    -nopad
   disable standard block padding

    -debug
   debug the BIOs used for I/O.

NOTES
    The program can be called either as openssl ciphername or openssl enc
    -ciphername.

    A password will be prompted for to derive the key and IV if necessary.

    The -salt option should ALWAYS be used if the key is being derived from
    a password unless you want compatibility with previous versions of
    OpenSSL and SSLeay.

    Without the -salt option it is possible to perform efficient dictionary
    attacks on the password and to attack stream cipher encrypted data. The
    reason for this is that without the salt the same password always gen-
    erates the same encryption key. When the salt is being used the first
    eight bytes of the encrypted data are reserved for the salt: it is gen-
    erated at random when encrypting a file and read from the encrypted
    file when it is decrypted.

    Some of the ciphers do not have large keys and others have security
    implications if not used correctly. A beginner is advised to just use a
    strong block cipher in CBC mode such as bf or des3.

    All the block ciphers normally use PKCS#5 padding also known as stan-
    dard block padding: this allows a rudimentary integrity or password
    check to be performed. However since the chance of random data passing
    the test is better than 1 in 256 it isn't a very good test.

    If padding is disabled then the input data must be a multiple of the
    cipher block length.

    All RC2 ciphers have the same key and effective key length.

    Blowfish and RC5 algorithms use a 128 bit key.

SUPPORTED CIPHERS
 base64    Base 64

 bf-cbc    Blowfish in CBC mode
 bf    Alias for bf-cbc
 bf-cfb    Blowfish in CFB mode
 bf-ecb    Blowfish in ECB mode
 bf-ofb    Blowfish in OFB mode

 cast-cbc   CAST in CBC mode
 cast    Alias for cast-cbc
 cast5-cbc   CAST5 in CBC mode
 cast5-cfb   CAST5 in CFB mode
 cast5-ecb   CAST5 in ECB mode
 cast5-ofb   CAST5 in OFB mode

 des-cbc    DES in CBC mode
 des    Alias for des-cbc
 des-cfb    DES in CBC mode
 des-ofb    DES in OFB mode
 des-ecb    DES in ECB mode

 des-ede-cbc   Two key triple DES EDE in CBC mode
 des-ede    Alias for des-ede
 des-ede-cfb   Two key triple DES EDE in CFB mode
 des-ede-ofb   Two key triple DES EDE in OFB mode

 des-ede3-cbc   Three key triple DES EDE in CBC mode
 des-ede3   Alias for des-ede3-cbc
 des3    Alias for des-ede3-cbc
 des-ede3-cfb   Three key triple DES EDE CFB mode
 des-ede3-ofb   Three key triple DES EDE in OFB mode

 desx    DESX algorithm.

 idea-cbc   IDEA algorithm in CBC mode
 idea    same as idea-cbc
 idea-cfb   IDEA in CFB mode
 idea-ecb   IDEA in ECB mode
 idea-ofb   IDEA in OFB mode

 rc2-cbc    128 bit RC2 in CBC mode
 rc2    Alias for rc2-cbc
 rc2-cfb    128 bit RC2 in CBC mode
 rc2-ecb    128 bit RC2 in CBC mode
 rc2-ofb    128 bit RC2 in CBC mode
 rc2-64-cbc   64 bit RC2 in CBC mode
 rc2-40-cbc   40 bit RC2 in CBC mode

 rc4    128 bit RC4
 rc4-64    64 bit RC4
 rc4-40    40 bit RC4

 rc5-cbc    RC5 cipher in CBC mode
 rc5    Alias for rc5-cbc
 rc5-cfb    RC5 cipher in CBC mode
 rc5-ecb    RC5 cipher in CBC mode
 rc5-ofb    RC5 cipher in CBC mode

EXAMPLES
    Just base64 encode a binary file:

 openssl base64 -in file.bin -out file.b64

    Decode the same file

 openssl base64 -d -in file.b64 -out file.bin

    Encrypt a file using triple DES in CBC mode using a prompted password:

 openssl des3 -salt -in file.txt -out file.des3

    Decrypt a file using a supplied password:

 openssl des3 -d -salt -in file.des3 -out file.txt -k mypassword

    Encrypt a file then base64 encode it (so it can be sent via mail for
    example) using Blowfish in CBC mode:

 openssl bf -a -salt -in file.txt -out file.bf

    Base64 decode a file then decrypt it:

 openssl bf -d -salt -a -in file.bf -out file.txt

    Decrypt some data using a supplied 40 bit RC4 key:

 openssl rc4-40 -in file.rc4 -out file.txt -K 0102030405

BUGS
    The -A option when used with large files doesn't work properly.

    There should be an option to allow an iteration count to be included.

    The enc program only supports a fixed number of algorithms with certain
    parameters. So if, for example, you want to use RC2 with a 76 bit key
    or RC4 with an 84 bit key you can't use this program.