MAN page from Trustix openssl-0.9.7e-8tr.i586.rpm

ENC

Section: OpenSSL (1)
Updated: 2004-08-18
Index

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 decryptedusing various block and stream ciphers using keys based on passwordsor explicitly provided. Base64 encoding or decoding can also be performedeither 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 argsee the PASS PHRASE ARGUMENTS section in openssl(1).
-salt: use a salt in the key derivation routines. This option should ALWAYSbe used unless compatibility with previous versions of OpenSSL or SSLeayis required. This option is only present on OpenSSL versions 0.9.5 orabove.
-nosalt: don't use a salt in the key derivation routines. This is the default forcompatibility 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 placethe data is base64 encoded after encryption. If decryption is set thenthe 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 previousversions 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 Superseded by the -pass argument.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 compatibility with previous versions of OpenSSL. Superseded bythe -pass argument.
-S salt: the actual salt to use: this must be represented as a string comprised onlyof hex digits.
-K key: the actual key to use: this must be represented as a string comprised onlyof hex digits. If only the key is specified, the IV must additionally specifiedusing the -iv option. When both a key and a password are specified, thekey given with the -K option will be used and the IV generated from thepassword will be taken. It probably does not make much sense to specifyboth key and password.
-iv IV: the actual IV to use: this must be represented as a string comprised onlyof hex digits. When only the key is specified using the -K option, theIV must explicitly be defined. When a password is being specified usingone 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 encryptionor 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 oropenssl 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 derivedfrom a password unless you want compatibility with previous versions ofOpenSSL and SSLeay.

Without the -salt option it is possible to perform efficient dictionaryattacks on the password and to attack stream cipher encrypted data. The reasonfor this is that without the salt the same password always generates the sameencryption key. When the salt is being used the first eight bytes of theencrypted data are reserved for the salt: it is generated at random whenencrypting a file and read from the encrypted file when it is decrypted.

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

All the block ciphers normally use PKCS#5 padding also known as standard blockpadding: this allows a rudimentary integrity or password check to beperformed. However since the chance of random data passing the test isbetter 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 cipherblock 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 withcertain parameters. So if, for example, you want to use RC2 with a76 bit key or RC4 with an 84 bit key you can't use this program.

This document was created byman2html,using the manual pages.