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333 lines
9.7 KiB
333 lines
9.7 KiB
=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/-base64>] |
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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<-S salt>] |
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[B<-salt>] |
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[B<-nosalt>] |
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[B<-z>] |
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[B<-md>] |
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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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[B<-none>] |
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[B<-engine id>] |
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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 is the default. |
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=item B<-nosalt> |
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don't use a salt in the key derivation routines. This option B<SHOULD NOT> be |
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used except for test purposes or compatibility with ancient versions of OpenSSL |
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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<-base64> |
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same as B<-a> |
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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<-nosalt> |
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do not use a salt |
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=item B<-salt> |
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use salt (randomly generated or provide with B<-S> option) when |
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encrypting (this is the default). |
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=item B<-S salt> |
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the actual salt to use: this must be represented as a string 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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=item B<-z> |
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Compress or decompress clear text using zlib before encryption or after |
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decryption. This option exists only if OpenSSL with compiled with zlib |
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or zlib-dynamic option. |
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=item B<-none> |
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Use NULL cipher (no encryption or decryption of input). |
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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>. But the first form doesn't work with |
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engine-provided ciphers, because this form is processed before the |
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configuration file is read and any ENGINEs loaded. |
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Engines which provide entirely new encryption algorithms (such as ccgost |
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engine which provides gost89 algorithm) should be configured in the |
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configuration file. Engines, specified in the command line using -engine |
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options can only be used for hadrware-assisted implementations of |
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ciphers, which are supported by OpenSSL core or other engine, specified |
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in the configuration file. |
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When enc command lists supported ciphers, ciphers provided by engines, |
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specified in the configuration files are listed too. |
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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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Note that some of these ciphers can be disabled at compile time |
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and some are available only if an appropriate engine is configured |
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in the configuration file. The output of the B<enc> command run with |
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unsupported options (for example B<openssl enc -help>) includes a |
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list of ciphers, supported by your versesion of OpenSSL, including |
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ones provided by configured engines. |
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The B<enc> program does not support authenticated encryption modes |
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like CCM and GCM. The utility does not store or retrieve the |
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authentication tag. |
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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 Two key triple DES EDE in ECB mode |
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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 Three key triple DES EDE in ECB mode |
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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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gost89 GOST 28147-89 in CFB mode (provided by ccgost engine) |
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gost89-cnt `GOST 28147-89 in CNT mode (provided by ccgost engine) |
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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 CFB mode |
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rc2-ecb 128 bit RC2 in ECB mode |
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rc2-ofb 128 bit RC2 in OFB 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 CFB mode |
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rc5-ecb RC5 cipher in ECB mode |
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rc5-ofb RC5 cipher in OFB mode |
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aes-[128|192|256]-cbc 128/192/256 bit AES in CBC mode |
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aes-[128|192|256] Alias for aes-[128|192|256]-cbc |
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aes-[128|192|256]-cfb 128/192/256 bit AES in 128 bit CFB mode |
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aes-[128|192|256]-cfb1 128/192/256 bit AES in 1 bit CFB mode |
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aes-[128|192|256]-cfb8 128/192/256 bit AES in 8 bit CFB mode |
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aes-[128|192|256]-ecb 128/192/256 bit AES in ECB mode |
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aes-[128|192|256]-ofb 128/192/256 bit AES in OFB 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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