enc.pod revision 109998
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<-nopad>] 25[B<-debug>] 26 27=head1 DESCRIPTION 28 29The symmetric cipher commands allow data to be encrypted or decrypted 30using various block and stream ciphers using keys based on passwords 31or explicitly provided. Base64 encoding or decoding can also be performed 32either by itself or in addition to the encryption or decryption. 33 34=head1 OPTIONS 35 36=over 4 37 38=item B<-in filename> 39 40the input filename, standard input by default. 41 42=item B<-out filename> 43 44the output filename, standard output by default. 45 46=item B<-pass arg> 47 48the password source. For more information about the format of B<arg> 49see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>. 50 51=item B<-salt> 52 53use a salt in the key derivation routines. This option should B<ALWAYS> 54be used unless compatibility with previous versions of OpenSSL or SSLeay 55is required. This option is only present on OpenSSL versions 0.9.5 or 56above. 57 58=item B<-nosalt> 59 60don't use a salt in the key derivation routines. This is the default for 61compatibility with previous versions of OpenSSL and SSLeay. 62 63=item B<-e> 64 65encrypt the input data: this is the default. 66 67=item B<-d> 68 69decrypt the input data. 70 71=item B<-a> 72 73base64 process the data. This means that if encryption is taking place 74the data is base64 encoded after encryption. If decryption is set then 75the input data is base64 decoded before being decrypted. 76 77=item B<-A> 78 79if the B<-a> option is set then base64 process the data on one line. 80 81=item B<-k password> 82 83the password to derive the key from. This is for compatibility with previous 84versions of OpenSSL. Superseded by the B<-pass> argument. 85 86=item B<-kfile filename> 87 88read the password to derive the key from the first line of B<filename>. 89This is for computability with previous versions of OpenSSL. Superseded by 90the B<-pass> argument. 91 92=item B<-S salt> 93 94the actual salt to use: this must be represented as a string comprised only 95of hex digits. 96 97=item B<-K key> 98 99the actual key to use: this must be represented as a string comprised only 100of hex digits. If only the key is specified, the IV must additionally specified 101using the B<-iv> option. When both a key and a password are specified, the 102key given with the B<-K> option will be used and the IV generated from the 103password will be taken. It probably does not make much sense to specify 104both key and password. 105 106=item B<-iv IV> 107 108the actual IV to use: this must be represented as a string comprised only 109of hex digits. When only the key is specified using the B<-K> option, the 110IV must explicitly be defined. When a password is being specified using 111one of the other options, the IV is generated from this password. 112 113=item B<-p> 114 115print out the key and IV used. 116 117=item B<-P> 118 119print out the key and IV used then immediately exit: don't do any encryption 120or decryption. 121 122=item B<-bufsize number> 123 124set the buffer size for I/O 125 126=item B<-nopad> 127 128disable standard block padding 129 130=item B<-debug> 131 132debug the BIOs used for I/O. 133 134=back 135 136=head1 NOTES 137 138The program can be called either as B<openssl ciphername> or 139B<openssl enc -ciphername>. 140 141A password will be prompted for to derive the key and IV if necessary. 142 143The B<-salt> option should B<ALWAYS> be used if the key is being derived 144from a password unless you want compatibility with previous versions of 145OpenSSL and SSLeay. 146 147Without the B<-salt> option it is possible to perform efficient dictionary 148attacks on the password and to attack stream cipher encrypted data. The reason 149for this is that without the salt the same password always generates the same 150encryption key. When the salt is being used the first eight bytes of the 151encrypted data are reserved for the salt: it is generated at random when 152encrypting a file and read from the encrypted file when it is decrypted. 153 154Some of the ciphers do not have large keys and others have security 155implications if not used correctly. A beginner is advised to just use 156a strong block cipher in CBC mode such as bf or des3. 157 158All the block ciphers normally use PKCS#5 padding also known as standard block 159padding: this allows a rudimentary integrity or password check to be 160performed. However since the chance of random data passing the test is 161better than 1 in 256 it isn't a very good test. 162 163If padding is disabled then the input data must be a multiple of the cipher 164block length. 165 166All RC2 ciphers have the same key and effective key length. 167 168Blowfish and RC5 algorithms use a 128 bit key. 169 170=head1 SUPPORTED CIPHERS 171 172 base64 Base 64 173 174 bf-cbc Blowfish in CBC mode 175 bf Alias for bf-cbc 176 bf-cfb Blowfish in CFB mode 177 bf-ecb Blowfish in ECB mode 178 bf-ofb Blowfish in OFB mode 179 180 cast-cbc CAST in CBC mode 181 cast Alias for cast-cbc 182 cast5-cbc CAST5 in CBC mode 183 cast5-cfb CAST5 in CFB mode 184 cast5-ecb CAST5 in ECB mode 185 cast5-ofb CAST5 in OFB mode 186 187 des-cbc DES in CBC mode 188 des Alias for des-cbc 189 des-cfb DES in CBC mode 190 des-ofb DES in OFB mode 191 des-ecb DES in ECB mode 192 193 des-ede-cbc Two key triple DES EDE in CBC mode 194 des-ede Alias for des-ede 195 des-ede-cfb Two key triple DES EDE in CFB mode 196 des-ede-ofb Two key triple DES EDE in OFB mode 197 198 des-ede3-cbc Three key triple DES EDE in CBC mode 199 des-ede3 Alias for des-ede3-cbc 200 des3 Alias for des-ede3-cbc 201 des-ede3-cfb Three key triple DES EDE CFB mode 202 des-ede3-ofb Three key triple DES EDE in OFB mode 203 204 desx DESX algorithm. 205 206 idea-cbc IDEA algorithm in CBC mode 207 idea same as idea-cbc 208 idea-cfb IDEA in CFB mode 209 idea-ecb IDEA in ECB mode 210 idea-ofb IDEA in OFB mode 211 212 rc2-cbc 128 bit RC2 in CBC mode 213 rc2 Alias for rc2-cbc 214 rc2-cfb 128 bit RC2 in CBC mode 215 rc2-ecb 128 bit RC2 in CBC mode 216 rc2-ofb 128 bit RC2 in CBC mode 217 rc2-64-cbc 64 bit RC2 in CBC mode 218 rc2-40-cbc 40 bit RC2 in CBC mode 219 220 rc4 128 bit RC4 221 rc4-64 64 bit RC4 222 rc4-40 40 bit RC4 223 224 rc5-cbc RC5 cipher in CBC mode 225 rc5 Alias for rc5-cbc 226 rc5-cfb RC5 cipher in CBC mode 227 rc5-ecb RC5 cipher in CBC mode 228 rc5-ofb RC5 cipher in CBC mode 229 230=head1 EXAMPLES 231 232Just base64 encode a binary file: 233 234 openssl base64 -in file.bin -out file.b64 235 236Decode the same file 237 238 openssl base64 -d -in file.b64 -out file.bin 239 240Encrypt a file using triple DES in CBC mode using a prompted password: 241 242 openssl des3 -salt -in file.txt -out file.des3 243 244Decrypt a file using a supplied password: 245 246 openssl des3 -d -salt -in file.des3 -out file.txt -k mypassword 247 248Encrypt a file then base64 encode it (so it can be sent via mail for example) 249using Blowfish in CBC mode: 250 251 openssl bf -a -salt -in file.txt -out file.bf 252 253Base64 decode a file then decrypt it: 254 255 openssl bf -d -salt -a -in file.bf -out file.txt 256 257Decrypt some data using a supplied 40 bit RC4 key: 258 259 openssl rc4-40 -in file.rc4 -out file.txt -K 0102030405 260 261=head1 BUGS 262 263The B<-A> option when used with large files doesn't work properly. 264 265There should be an option to allow an iteration count to be included. 266 267The B<enc> program only supports a fixed number of algorithms with 268certain parameters. So if, for example, you want to use RC2 with a 26976 bit key or RC4 with an 84 bit key you can't use this program. 270 271=cut 272