271 lines
7.6 KiB
Text
271 lines
7.6 KiB
Text
=pod
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=head1 NAME
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enc - symmetric cipher routines
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=head1 SYNOPSIS
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B<openssl enc -ciphername>
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[B<-in filename>]
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[B<-out filename>]
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[B<-pass arg>]
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[B<-e>]
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[B<-d>]
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[B<-a>]
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[B<-A>]
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[B<-k password>]
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[B<-kfile filename>]
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[B<-K key>]
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[B<-iv IV>]
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[B<-p>]
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[B<-P>]
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[B<-bufsize number>]
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[B<-nopad>]
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[B<-debug>]
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=head1 DESCRIPTION
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The symmetric cipher commands allow data to be encrypted or decrypted
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using various block and stream ciphers using keys based on passwords
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or explicitly provided. Base64 encoding or decoding can also be performed
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either by itself or in addition to the encryption or decryption.
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=head1 OPTIONS
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=over 4
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=item B<-in filename>
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the input filename, standard input by default.
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=item B<-out filename>
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the output filename, standard output by default.
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=item B<-pass arg>
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the password source. For more information about the format of B<arg>
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see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
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=item B<-salt>
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use a salt in the key derivation routines. This option should B<ALWAYS>
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be used unless compatibility with previous versions of OpenSSL or SSLeay
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is required. This option is only present on OpenSSL versions 0.9.5 or
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above.
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=item B<-nosalt>
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don't use a salt in the key derivation routines. This is the default for
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compatibility with previous versions of OpenSSL and SSLeay.
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=item B<-e>
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encrypt the input data: this is the default.
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=item B<-d>
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decrypt the input data.
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=item B<-a>
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base64 process the data. This means that if encryption is taking place
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the data is base64 encoded after encryption. If decryption is set then
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the input data is base64 decoded before being decrypted.
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=item B<-A>
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if the B<-a> option is set then base64 process the data on one line.
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=item B<-k password>
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the password to derive the key from. This is for compatibility with previous
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versions of OpenSSL. Superseded by the B<-pass> argument.
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=item B<-kfile filename>
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read the password to derive the key from the first line of B<filename>.
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This is for compatibility with previous versions of OpenSSL. Superseded by
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the B<-pass> argument.
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=item B<-S salt>
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the actual salt to use: this must be represented as a string comprised only
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of hex digits.
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=item B<-K key>
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the actual key to use: this must be represented as a string comprised only
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of hex digits. If only the key is specified, the IV must additionally specified
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using the B<-iv> option. When both a key and a password are specified, the
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key given with the B<-K> option will be used and the IV generated from the
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password will be taken. It probably does not make much sense to specify
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both key and password.
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=item B<-iv IV>
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the actual IV to use: this must be represented as a string comprised only
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of hex digits. When only the key is specified using the B<-K> option, the
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IV must explicitly be defined. When a password is being specified using
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one of the other options, the IV is generated from this password.
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=item B<-p>
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print out the key and IV used.
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=item B<-P>
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print out the key and IV used then immediately exit: don't do any encryption
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or decryption.
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=item B<-bufsize number>
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set the buffer size for I/O
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=item B<-nopad>
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disable standard block padding
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=item B<-debug>
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debug the BIOs used for I/O.
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=back
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=head1 NOTES
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The program can be called either as B<openssl ciphername> or
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B<openssl enc -ciphername>.
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A password will be prompted for to derive the key and IV if necessary.
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The B<-salt> option should B<ALWAYS> be used if the key is being derived
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from a password unless you want compatibility with previous versions of
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OpenSSL and SSLeay.
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Without the B<-salt> option it is possible to perform efficient dictionary
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attacks on the password and to attack stream cipher encrypted data. The reason
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for this is that without the salt the same password always generates the same
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encryption key. When the salt is being used the first eight bytes of the
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encrypted data are reserved for the salt: it is generated at random when
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encrypting a file and read from the encrypted file when it is decrypted.
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Some of the ciphers do not have large keys and others have security
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implications if not used correctly. A beginner is advised to just use
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a strong block cipher in CBC mode such as bf or des3.
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All the block ciphers normally use PKCS#5 padding also known as standard block
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padding: this allows a rudimentary integrity or password check to be
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performed. However since the chance of random data passing the test is
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better than 1 in 256 it isn't a very good test.
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If padding is disabled then the input data must be a multiple of the cipher
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block length.
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All RC2 ciphers have the same key and effective key length.
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Blowfish and RC5 algorithms use a 128 bit key.
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=head1 SUPPORTED CIPHERS
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base64 Base 64
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bf-cbc Blowfish in CBC mode
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bf Alias for bf-cbc
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bf-cfb Blowfish in CFB mode
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bf-ecb Blowfish in ECB mode
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bf-ofb Blowfish in OFB mode
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cast-cbc CAST in CBC mode
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cast Alias for cast-cbc
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cast5-cbc CAST5 in CBC mode
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cast5-cfb CAST5 in CFB mode
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cast5-ecb CAST5 in ECB mode
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cast5-ofb CAST5 in OFB mode
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des-cbc DES in CBC mode
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des Alias for des-cbc
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des-cfb DES in CBC mode
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des-ofb DES in OFB mode
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des-ecb DES in ECB mode
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des-ede-cbc Two key triple DES EDE in CBC mode
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des-ede Alias for des-ede
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des-ede-cfb Two key triple DES EDE in CFB mode
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des-ede-ofb Two key triple DES EDE in OFB mode
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des-ede3-cbc Three key triple DES EDE in CBC mode
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des-ede3 Alias for des-ede3-cbc
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des3 Alias for des-ede3-cbc
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des-ede3-cfb Three key triple DES EDE CFB mode
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des-ede3-ofb Three key triple DES EDE in OFB mode
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desx DESX algorithm.
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idea-cbc IDEA algorithm in CBC mode
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idea same as idea-cbc
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idea-cfb IDEA in CFB mode
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idea-ecb IDEA in ECB mode
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idea-ofb IDEA in OFB mode
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rc2-cbc 128 bit RC2 in CBC mode
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rc2 Alias for rc2-cbc
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rc2-cfb 128 bit RC2 in CBC mode
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rc2-ecb 128 bit RC2 in CBC mode
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rc2-ofb 128 bit RC2 in CBC mode
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rc2-64-cbc 64 bit RC2 in CBC mode
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rc2-40-cbc 40 bit RC2 in CBC mode
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rc4 128 bit RC4
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rc4-64 64 bit RC4
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rc4-40 40 bit RC4
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rc5-cbc RC5 cipher in CBC mode
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rc5 Alias for rc5-cbc
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rc5-cfb RC5 cipher in CBC mode
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rc5-ecb RC5 cipher in CBC mode
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rc5-ofb RC5 cipher in CBC mode
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=head1 EXAMPLES
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Just base64 encode a binary file:
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openssl base64 -in file.bin -out file.b64
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Decode the same file
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openssl base64 -d -in file.b64 -out file.bin
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Encrypt a file using triple DES in CBC mode using a prompted password:
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openssl des3 -salt -in file.txt -out file.des3
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Decrypt a file using a supplied password:
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openssl des3 -d -salt -in file.des3 -out file.txt -k mypassword
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Encrypt a file then base64 encode it (so it can be sent via mail for example)
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using Blowfish in CBC mode:
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openssl bf -a -salt -in file.txt -out file.bf
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Base64 decode a file then decrypt it:
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openssl bf -d -salt -a -in file.bf -out file.txt
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Decrypt some data using a supplied 40 bit RC4 key:
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openssl rc4-40 -in file.rc4 -out file.txt -K 0102030405
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=head1 BUGS
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The B<-A> option when used with large files doesn't work properly.
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There should be an option to allow an iteration count to be included.
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The B<enc> program only supports a fixed number of algorithms with
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certain parameters. So if, for example, you want to use RC2 with a
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76 bit key or RC4 with an 84 bit key you can't use this program.
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=cut
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