enc
ENC(1) OpenSSL ENC(1) NAME enc - symmetric cipher routines SYNOPSIS openssl enc -ciphername [-in filename] [-out filename] [-pass arg] [-e] [-d] [-a] [-A] [-k password] [-kfile filename] [-K key] [-iv IV] [-p] [-P] [-bufsize number] [-debug] DESCRIPTION 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. OPTIONS -in filename the input filename, standard input by default. -out filename the output filename, standard output by default. -pass arg the password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl(1). -salt use a salt in the key derivation routines. This option should 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. -nosalt don't use a salt in the key derivation routines. This is the default for compatibility with previous versions of OpenSSL and SSLeay. -e encrypt the input data: this is the default. -d decrypt the input data. -a base64 process the data. This means that if encryption is taking place the data is base64 encoded after encryption. If decryption is set then the input data is base64 decoded before being decrypted. -A if the -a option is set then base64 process the data on one line. -k password the password to derive the key from. This is for compatibility with previous versions of OpenSSL. Superseded by the -pass argument. -kfile filename read the password to derive the key from the first line of filename. This is for computability with previous versions of OpenSSL. Superseded by the -pass argument. -S salt the actual salt to use: this must be represented as a string comprised only of hex digits. -K key the actual key to use: this must be represented as a string comprised only of hex digits. If only the key is specified, the IV must additionally specified using the -iv option. When both a key and a password are specified, the key given with the -K option will be used and the IV generated from the password will be taken. It probably does not make much sense to specify both key and password. -iv IV the actual IV to use: this must be represented as a string comprised only of hex digits. When only the key is specified using the -K option, the IV must explicitly be defined. When a password is being specified using one of the other options, the IV is generated from this password. -p print out the key and IV used. -P print out the key and IV used then immediately exit: don't do any encryption or decryption. -bufsize number set the buffer size for I/O -debug debug the BIOs used for I/O. NOTES The program can be called either as openssl ciphername or openssl enc -ciphername. A password will be prompted for to derive the key and IV if necessary. The -salt option should 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 -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 better than 1 in 256 it isn't a very good test. All RC2 ciphers have the same key and effective key length. Blowfish and RC5 algorithms use a 128 bit key. SUPPORTED CIPHERS base64 Base 64 bf-cbc Blowfish in CBC mode bf Alias for bf-cbc bf-cfb Blowfish in CFB mode bf-ecb Blowfish in ECB mode bf-ofb Blowfish in OFB mode cast-cbc CAST in CBC mode cast Alias for cast-cbc cast5-cbc CAST5 in CBC mode cast5-cfb CAST5 in CFB mode cast5-ecb CAST5 in ECB mode cast5-ofb CAST5 in OFB mode des-cbc DES in CBC mode des Alias for des-cbc des-cfb DES in CBC mode des-ofb DES in OFB mode des-ecb DES in ECB mode des-ede-cbc Two key triple DES EDE in CBC mode des-ede Alias for des-ede des-ede-cfb Two key triple DES EDE in CFB mode des-ede-ofb Two key triple DES EDE in OFB mode des-ede3-cbc Three key triple DES EDE in CBC mode des-ede3 Alias for des-ede3-cbc des3 Alias for des-ede3-cbc des-ede3-cfb Three key triple DES EDE CFB mode des-ede3-ofb Three key triple DES EDE in OFB mode desx DESX algorithm. idea-cbc IDEA algorithm in CBC mode idea same as idea-cbc idea-cfb IDEA in CFB mode idea-ecb IDEA in ECB mode idea-ofb IDEA in OFB mode rc2-cbc 128 bit RC2 in CBC mode rc2 Alias for rc2-cbc rc2-cfb 128 bit RC2 in CBC mode rc2-ecb 128 bit RC2 in CBC mode rc2-ofb 128 bit RC2 in CBC mode rc2-64-cbc 64 bit RC2 in CBC mode rc2-40-cbc 40 bit RC2 in CBC mode rc4 128 bit RC4 rc4-64 64 bit RC4 rc4-40 40 bit RC4 rc5-cbc RC5 cipher in CBC mode rc5 Alias for rc5-cbc rc5-cfb RC5 cipher in CBC mode rc5-ecb RC5 cipher in CBC mode rc5-ofb RC5 cipher in CBC mode EXAMPLES 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 BUGS The -A option when used with large files doesn't work properly. There should be an option to allow an iteration count to be included. Like the EVP library the enc program only supports a fixed number of algorithms with certain parameters. So if, for example, you want to use RC2 with a 76 bit key or RC4 with an 84 bit key you can't use this program. 9/Jul/2001 0.9.6b ENC(1)