enc



ENC(1)                              OpenSSL                             ENC(1)




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 Superseded by the -pass argument.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 compatibility 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           Superseded by the -pass argument.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.



0.9.7f                            2004-08-18                            ENC(1)

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