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Manpages ENCSection: OpenSSL (1ssl)Updated: 0.9.6c Index Return to Main Contents NAMEenc - symmetric cipher routinesSYNOPSISopenssl 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]DESCRIPTIONThe 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
NOTESThe 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 EXAMPLESJust base64 encode a binary file:
openssl base64 -in file.bin -out file.b64Decode the same file
openssl base64 -d -in file.b64 -out file.binEncrypt a file using triple DES in CBC mode using a prompted password:
openssl des3 -salt -in file.txt -out file.des3Decrypt a file using a supplied password:
openssl des3 -d -salt -in file.des3 -out file.txt -k mypasswordEncrypt 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.bfBase64 decode a file then decrypt it:
openssl bf -d -salt -a -in file.bf -out file.txtDecrypt some data using a supplied 40 bit RC4 key:
openssl rc4-40 -in file.rc4 -out file.txt -K 0102030405 BUGSThe -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.
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