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 Superseded by the -pass argument.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 filename.  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	   Superseded by the -pass argument.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 comprised only of hex digits.

       -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 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.

       -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 generates 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 generated 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 standard 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.

0.9.7d								    2003-11-20								    ENC(1)