enc.pod revision 59191 
1=pod
2
3=head1 NAME
4
5enc - symmetric cipher routines
6
7=head1 SYNOPSIS
8
9B<openssl enc -ciphername>
10[B<-in filename>]
11[B<-out filename>]
12[B<-pass arg>]
13[B<-e>]
14[B<-d>]
15[B<-a>]
16[B<-A>]
17[B<-k password>]
18[B<-kfile filename>]
19[B<-K key>]
20[B<-iv IV>]
21[B<-p>]
22[B<-P>]
23[B<-bufsize number>]
24[B<-debug>]
25
26=head1 DESCRIPTION
27
28The symmetric cipher commands allow data to be encrypted or decrypted
29using various block and stream ciphers using keys based on passwords
30or explicitly provided. Base64 encoding or decoding can also be performed
31either by itself or in addition to the encryption or decryption.
32
33=head1 OPTIONS
34
35=over 4
36
37=item B<-in filename>
38
39the input filename, standard input by default.
40
41=item B<-out filename>
42
43the output filename, standard output by default.
44
45=item B<-pass arg>
46
47the password source. For more information about the format of B<arg>
48see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
49
50=item B<-salt>
51
52use a salt in the key derivation routines. This option should B<ALWAYS>
53be used unless compatibility with previous versions of OpenSSL or SSLeay
54is required. This option is only present on OpenSSL versions 0.9.5 or
55above.
56
57=item B<-nosalt>
58
59don't use a salt in the key derivation routines. This is the default for
60compatibility with previous versions of OpenSSL and SSLeay.
61
62=item B<-e>
63
64encrypt the input data: this is the default.
65
66=item B<-d>
67
68decrypt the input data.
69
70=item B<-a>
71
72base64 process the data. This means that if encryption is taking place
73the data is base64 encoded after encryption. If decryption is set then
74the input data is base64 decoded before being decrypted.
75
76=item B<-A>
77
78if the B<-a> option is set then base64 process the data on one line.
79
80=item B<-k password>
81
82the password to derive the key from. This is for compatibility with previous
83versions of OpenSSL. Superseded by the B<-pass> argument.
84
85=item B<-kfile filename>
86
87read the password to derive the key from the first line of B<filename>.
88This is for computability with previous versions of OpenSSL. Superseded by
89the B<-pass> argument.
90
91=item B<-S salt>
92
93the actual salt to use: this must be represented as a string comprised only
94of hex digits.
95
96=item B<-K key>
97
98the actual key to use: this must be represented as a string comprised only
99of hex digits.
100
101=item B<-iv IV>
102
103the actual IV to use: this must be represented as a string comprised only
104of hex digits.
105
106=item B<-p>
107
108print out the key and IV used.
109
110=item B<-P>
111
112print out the key and IV used then immediately exit: don't do any encryption
113or decryption.
114
115=item B<-bufsize number>
116
117set the buffer size for I/O
118
119=item B<-debug>
120
121debug the BIOs used for I/O.
122
123=back
124
125=head1 NOTES
126
127The program can be called either as B<openssl ciphername> or
128B<openssl enc -ciphername>.
129
130A password will be prompted for to derive the key and IV if necessary.
131
132The B<-salt> option should B<ALWAYS> be used if the key is being derived
133from a password unless you want compatibility with previous versions of
134OpenSSL and SSLeay.
135
136Without the B<-salt> option it is possible to perform efficient dictionary
137attacks on the password and to attack stream cipher encrypted data. The reason
138for this is that without the salt the same password always generates the same
139encryption key. When the salt is being used the first eight bytes of the
140encrypted data are reserved for the salt: it is generated at random when
141encrypting a file and read from the encrypted file when it is decrypted.
142
143Some of the ciphers do not have large keys and others have security
144implications if not used correctly. A beginner is advised to just use
145a strong block cipher in CBC mode such as bf or des3.
146
147All the block ciphers use PKCS#5 padding also known as standard block
148padding: this allows a rudimentary integrity or password check to be
149performed. However since the chance of random data passing the test is
150better than 1 in 256 it isn't a very good test.
151
152All RC2 ciphers have the same key and effective key length.
153
154Blowfish and RC5 algorithms use a 128 bit key.
155
156=head1 SUPPORTED CIPHERS
157
158 base64             Base 64
159
160 bf-cbc             Blowfish in CBC mode
161 bf                 Alias for bf-cbc
162 bf-cfb             Blowfish in CFB mode
163 bf-ecb             Blowfish in ECB mode
164 bf-ofb             Blowfish in OFB mode
165
166 cast-cbc           CAST in CBC mode
167 cast               Alias for cast-cbc
168 cast5-cbc          CAST5 in CBC mode
169 cast5-cfb          CAST5 in CFB mode
170 cast5-ecb          CAST5 in ECB mode
171 cast5-ofb          CAST5 in OFB mode
172
173 des-cbc            DES in CBC mode
174 des                Alias for des-cbc
175 des-cfb            DES in CBC mode
176 des-ofb            DES in OFB mode
177 des-ecb            DES in ECB mode
178
179 des-ede-cbc        Two key triple DES EDE in CBC mode
180 des-ede            Alias for des-ede
181 des-ede-cfb        Two key triple DES EDE in CFB mode
182 des-ede-ofb        Two key triple DES EDE in OFB mode
183
184 des-ede3-cbc       Three key triple DES EDE in CBC mode
185 des-ede3           Alias for des-ede3-cbc
186 des3               Alias for des-ede3-cbc
187 des-ede3-cfb       Three key triple DES EDE CFB mode
188 des-ede3-ofb       Three key triple DES EDE in OFB mode
189
190 desx               DESX algorithm.
191
192 idea-cbc           IDEA algorithm in CBC mode
193 idea               same as idea-cbc
194 idea-cfb           IDEA in CFB mode
195 idea-ecb           IDEA in ECB mode
196 idea-ofb           IDEA in OFB mode
197
198 rc2-cbc            128 bit RC2 in CBC mode
199 rc2                Alias for rc2-cbc
200 rc2-cfb            128 bit RC2 in CBC mode
201 rc2-ecb            128 bit RC2 in CBC mode
202 rc2-ofb            128 bit RC2 in CBC mode
203 rc2-64-cbc         64 bit RC2 in CBC mode
204 rc2-40-cbc         40 bit RC2 in CBC mode
205
206 rc4                128 bit RC4
207 rc4-64             64 bit RC4
208 rc4-40             40 bit RC4
209
210 rc5-cbc            RC5 cipher in CBC mode
211 rc5                Alias for rc5-cbc
212 rc5-cfb            RC5 cipher in CBC mode
213 rc5-ecb            RC5 cipher in CBC mode
214 rc5-ofb            RC5 cipher in CBC mode
215
216=head1 EXAMPLES
217
218Just base64 encode a binary file:
219
220 openssl base64 -in file.bin -out file.b64
221
222Decode the same file
223
224 openssl base64 -d -in file.b64 -out file.bin 
225
226Encrypt a file using triple DES in CBC mode using a prompted password:
227
228 openssl des3 -salt -in file.txt -out file.des3 
229
230Decrypt a file using a supplied password:
231
232 openssl des3 -d -salt -in file.des3 -out file.txt -k mypassword
233
234Encrypt a file then base64 encode it (so it can be sent via mail for example)
235using Blowfish in CBC mode:
236
237 openssl bf -a -salt -in file.txt -out file.bf
238
239Base64 decode a file then decrypt it:
240
241 openssl bf -d -salt -a -in file.bf -out file.txt
242
243Decrypt some data using a supplied 40 bit RC4 key:
244
245 openssl rc4-40 -in file.rc4 -out file.txt -K 0102030405
246
247=head1 BUGS
248
249The B<-A> option when used with large files doesn't work properly.
250
251There should be an option to allow an iteration count to be included.
252
253Like the EVP library the B<enc> program only supports a fixed number of
254algorithms with certain parameters. So if, for example, you want to use RC2
255with a 76 bit key or RC4 with an 84 bit key you can't use this program.
256
257=cut
258