=pod
+
=head1 NAME
enc - symmetric cipher routines
=head1 DESCRIPTION
-The symmetric cipher commands allow data to be encrytped or decrypted
+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.
the output filename, standard output by default.
+=item B<-salt>
+
+use a salt in the key derivation routines. This option should B<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.
+
+=item B<-nosalt>
+
+don't use a salt in the key derivation routines. This is the default for
+compatibility with previous versions of OpenSSL and SSLeay.
+
=item B<-e>
encrypt the input data: this is the default.
read the password to derive the key from the first line of B<filename>
+=item B<-S salt>
+
+the actual salt to use: this must be represented as a string comprised only
+of hex digits.
+
=item B<-K key>
the actual key to use: this must be represented as a string comprised only
A password will be prompted for to derive the key and IV if necessary.
+The B<-salt> option should B<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 B<-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 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
bf-cbc Blowfish in CBC mode
bf Alias for bf-cbc
- bf-cfb Blowish in CFB mode
+ bf-cfb Blowfish in CFB mode
bf-ecb Blowfish in ECB mode
bf-ofb Blowfish in OFB mode
=head1 EXAMPLES
-To be added....
+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
=head1 BUGS
The B<-A> option when used with large files doesn't work properly.
-The key derivation algorithm used is compatible with the SSLeay algorithm. It
-is not very good: it uses unsalted MD5. There should be an option to allow a
-salt or iteration count to be included.
+There should be an option to allow an iteration count to be included.
Like the EVP library the B<enc> program only supports a fixed number of
algorithms with certain parameters. So if, for example, you want to use RC2
projects / oweals / openssl.git / blobdiff