enc.pod revision 79998
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 Superseded by the B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 Superseded by 89the B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. If only the key is specified, the IV must additionally specified 100using the B<-iv> option. When both a key and a password are specified, the 101key given with the B<-K> option will be used and the IV generated from the 102password will be taken. It probably does not make much sense to specify 103both key and password. 104 105=item B<-iv IV> 106 107the actual IV to use: this must be represented as a string comprised only 108of hex digits. When only the key is specified using the B<-K> option, the 109IV must explicitly be defined. When a password is being specified using 110one of the other options, the IV is generated from this password. 111 112=item B<-p> 113 114print out the key and IV used. 115 116=item B<-P> 117 118print out the key and IV used then immediately exit: don't do any encryption 119or decryption. 120 121=item B<-bufsize number> 122 123set the buffer size for I/O 124 125=item B<-debug> 126 127debug the BIOs used for I/O. 128 129=back 130 131=head1 NOTES 132 133The program can be called either as B<openssl ciphername> or 134B<openssl enc -ciphername>. 135 136A password will be prompted for to derive the key and IV if necessary. 137 138The B<-salt> option should B<ALWAYS> be used if the key is being derived 139from a password unless you want compatibility with previous versions of 140OpenSSL and SSLeay. 141 142Without the B<-salt> option it is possible to perform efficient dictionary 143attacks on the password and to attack stream cipher encrypted data. The reason 144for this is that without the salt the same password always generates the same 145encryption key. When the salt is being used the first eight bytes of the 146encrypted data are reserved for the salt: it is generated at random when 147encrypting a file and read from the encrypted file when it is decrypted. 148 149Some of the ciphers do not have large keys and others have security 150implications if not used correctly. A beginner is advised to just use 151a strong block cipher in CBC mode such as bf or des3. 152 153All the block ciphers use PKCS#5 padding also known as standard block 154padding: this allows a rudimentary integrity or password check to be 155performed. However since the chance of random data passing the test is 156better than 1 in 256 it isn't a very good test. 157 158All RC2 ciphers have the same key and effective key length. 159 160Blowfish and RC5 algorithms use a 128 bit key. 161 162=head1 SUPPORTED CIPHERS 163 164 base64 Base 64 165 166 bf-cbc Blowfish in CBC mode 167 bf Alias for bf-cbc 168 bf-cfb Blowfish in CFB mode 169 bf-ecb Blowfish in ECB mode 170 bf-ofb Blowfish in OFB mode 171 172 cast-cbc CAST in CBC mode 173 cast Alias for cast-cbc 174 cast5-cbc CAST5 in CBC mode 175 cast5-cfb CAST5 in CFB mode 176 cast5-ecb CAST5 in ECB mode 177 cast5-ofb CAST5 in OFB mode 178 179 des-cbc DES in CBC mode 180 des Alias for des-cbc 181 des-cfb DES in CBC mode 182 des-ofb DES in OFB mode 183 des-ecb DES in ECB mode 184 185 des-ede-cbc Two key triple DES EDE in CBC mode 186 des-ede Alias for des-ede 187 des-ede-cfb Two key triple DES EDE in CFB mode 188 des-ede-ofb Two key triple DES EDE in OFB mode 189 190 des-ede3-cbc Three key triple DES EDE in CBC mode 191 des-ede3 Alias for des-ede3-cbc 192 des3 Alias for des-ede3-cbc 193 des-ede3-cfb Three key triple DES EDE CFB mode 194 des-ede3-ofb Three key triple DES EDE in OFB mode 195 196 desx DESX algorithm. 197 198 idea-cbc IDEA algorithm in CBC mode 199 idea same as idea-cbc 200 idea-cfb IDEA in CFB mode 201 idea-ecb IDEA in ECB mode 202 idea-ofb IDEA in OFB mode 203 204 rc2-cbc 128 bit RC2 in CBC mode 205 rc2 Alias for rc2-cbc 206 rc2-cfb 128 bit RC2 in CBC mode 207 rc2-ecb 128 bit RC2 in CBC mode 208 rc2-ofb 128 bit RC2 in CBC mode 209 rc2-64-cbc 64 bit RC2 in CBC mode 210 rc2-40-cbc 40 bit RC2 in CBC mode 211 212 rc4 128 bit RC4 213 rc4-64 64 bit RC4 214 rc4-40 40 bit RC4 215 216 rc5-cbc RC5 cipher in CBC mode 217 rc5 Alias for rc5-cbc 218 rc5-cfb RC5 cipher in CBC mode 219 rc5-ecb RC5 cipher in CBC mode 220 rc5-ofb RC5 cipher in CBC mode 221 222=head1 EXAMPLES 223 224Just base64 encode a binary file: 225 226 openssl base64 -in file.bin -out file.b64 227 228Decode the same file 229 230 openssl base64 -d -in file.b64 -out file.bin 231 232Encrypt a file using triple DES in CBC mode using a prompted password: 233 234 openssl des3 -salt -in file.txt -out file.des3 235 236Decrypt a file using a supplied password: 237 238 openssl des3 -d -salt -in file.des3 -out file.txt -k mypassword 239 240Encrypt a file then base64 encode it (so it can be sent via mail for example) 241using Blowfish in CBC mode: 242 243 openssl bf -a -salt -in file.txt -out file.bf 244 245Base64 decode a file then decrypt it: 246 247 openssl bf -d -salt -a -in file.bf -out file.txt 248 249Decrypt some data using a supplied 40 bit RC4 key: 250 251 openssl rc4-40 -in file.rc4 -out file.txt -K 0102030405 252 253=head1 BUGS 254 255The B<-A> option when used with large files doesn't work properly. 256 257There should be an option to allow an iteration count to be included. 258 259Like the EVP library the B<enc> program only supports a fixed number of 260algorithms with certain parameters. So if, for example, you want to use RC2 261with a 76 bit key or RC4 with an 84 bit key you can't use this program. 262 263=cut 264