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Full Discussion: which encryption method?
Top Forums Shell Programming and Scripting which encryption method? Post 25561 by kjd on Wednesday 31st of July 2002 09:07:36 PM
Old 07-31-2002
Comparison or storage for later use?

If you're storing for comparison (authentication) purposes (e.g. user enters a password, you save it, then later ask for the password again for verification), then you can store an MD5 hash of the password rather than encrypting and storing the password itself. See Digest::MD5 or Digest::Perl::MD5. Use the second if you are unable to compile C code; it is slower, but should not be noticably slow for something small like passwords.

Using this method, you would take input from the user, and hash it with MD5. The output is a unique string that cannot be reversed to re-obtain the original data. This is useful for password comparison because you can hash the input from the user, then compare the stored value and new value to assure they are the same. The password never has to be stored.

If you're storing for later retrieval and usage then you need a form of encryption that you can reverse with a key. You would use this for encrypting files/data, such as a list of passwords that you want to store for use later. Try Rijndael, Blowfish, Twofish. Of course you need to obtain the key somehow, probably by prompting the user at run-time.

Last edited by kjd; 07-31-2002 at 10:33 PM..
 

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DOVEADM-PW(1)							      Dovecot							     DOVEADM-PW(1)

NAME
doveadm-pw - Dovecot's password hash generator SYNOPSIS
doveadm [-Dv] pw -l doveadm [-Dv] pw [-p password] [-r rounds] [-s scheme] [-u user] [-V] doveadm [-Dv] pw -t hash [-u user] DESCRIPTION
doveadm pw is used to generate password hashes for different password schemes and optionally verify the generated hash. All generated password hashes have a {scheme} prefix, for example {SHA512-CRYPT.HEX}. All passdbs have a default scheme for passwords stored without the {scheme} prefix. The default scheme can be overridden by storing the password with the scheme prefix. OPTIONS
Global doveadm(1) options: -D Enables verbosity and debug messages. -v Enables verbosity, including progress counter. Command specific options: -l List all supported password schemes and exit successfully. There are up to three optional password schemes: BLF-CRYPT (Blowfish crypt), SHA256-CRYPT and SHA512-CRYPT. Their availability depends on the system's currently used libc. -p password The plain text password for which the hash should be generated. If no password was given doveadm(1) will prompt interactively for one. -r rounds The password schemes BLF-CRYPT, SHA256-CRYPT and SHA512-CRYPT supports a variable number of encryption rounds. The following table shows the minimum/maximum number of encryption rounds per scheme. When the -r option was omitted the default number of encryption rounds will be applied. Scheme | Minimum | Maximum | Default ---------------------------------------------- BLF-CRYPT | 4 | 31 | 5 SHA256-CRYPT | 1000 | 999999999 | 5000 SHA512-CRYPT | 1000 | 999999999 | 5000 -s scheme The password scheme which should be used to generate the hashed password. By default the CRAM-MD5 scheme will be used. It is also possible to append an encoding suffix to the scheme. Supported encoding suffixes are: .b64, .base64 and .hex. See also http://wiki2.dovecot.org/Authentication/PasswordSchemes for more details about password schemes. -t hash Test if the given password hash matches a given plain text password. -u user When the DIGEST-MD5 scheme is used, also the user name must be given, because the user name is a part of the generated hash. For more information about Digest-MD5 please read also: http://wiki2.dovecot.org/Authentication/Mechanisms/DigestMD5 -V When this option is given, the hashed password will be internally verified. The result of the verification will be shown after the hashed password, enclosed in parenthesis. EXAMPLE
The first password hash is a DIGEST-MD5 hash for jane.roe@example.com. The second password hash is a CRAM-MD5 hash for john.doe@exam- ple.com. doveadm pw -s digest-md5 -u jane.roe@example.com Enter new password: Retype new password: {DIGEST-MD5}9b9dcb4466233a9307bbc33708dffda0 doveadm pw Enter new password: Retype new password: {CRAM-MD5}913331d8782236a8ecba7764a63aa27b26437fd40ca878d887f11d81245c2c6b REPORTING BUGS
Report bugs, including doveconf -n output, to the Dovecot Mailing List <dovecot@dovecot.org>. Information about reporting bugs is avail- able at: http://dovecot.org/bugreport.html SEE ALSO
doveadm(1) Dovecot v2.1 2012-02-13 DOVEADM-PW(1)
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