Using Win32 functions in Visual FoxPro Image Gallery
Code examples:
Custom FTP Class for Visual FoxPro application
Displaying the associated icons and descriptions for files and folders
How to download a file from the FTP server using FtpGetFile
Placing On-screen Alert on top of all windows
Attaching menu to a top-level form
Enumerating data formats currently available on the clipboard
Finding out if the current user is the Guest account
How to print FoxPro form
Peer-to-peer LAN messenger built with Mailslot API functions
The SQLGetProp() creates a bridge between Visual FoxPro and the ODBC API
Creating irregularly shaped FoxPro form using transparency color key
Vertical Label control
GDI+: sending image of FoxPro form to printer
How to draw custom Window Caption on FoxPro form
Drawing a window caption using the DrawCaption routine
How to make application automatically close all documents it opened
GDI+: saving image of FoxPro form to graphics file (BMP, GIF, JPG, PNG, TIF)
How to display a user-defined icon in the MessageBox dialog
How to display the Properties dialog box for a file (ShellExecuteEx)
Transparent Menu Class (requires VFP9)
Enumerating print jobs and retrieving information for default printer (JOB_INFO_1 structures)
GDI+: printing vertical text on VFP reports via generated images (VFP9)
Starting an external application in VFP using WinExec
Using an Event Object. Part A: running an application that creates an Event object
How to create MD-5 and SHA-1 hash values from a string

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Before you begin:
Test the presented class as follows:
obj = CREATEOBJECT("TheHash")

? obj.CreateSHA1("test string")

* returns 661295C9CBF9D6B2F6428414504A8DEED3020641

? obj.CreateMD5("test string")
* returns 6F8DB599DE986FAB7A21625B7916589C

See also:
  • Simple class that encrypts and decrypts files using Cryptography API Functions
  • CryptoAPI: Collection of Providers class
  • WinINet function CreateMD5SSOHash
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    3548 bytes  
    Created: 2005-03-07 15:21:11  
    Modified: 2013-09-20 13:30:28  
    Visits in 7 days: 119  
    Listed functions:
    CryptAcquireContext
    CryptCreateHash
    CryptDestroyHash
    CryptGetHashParam
    CryptHashData
    CryptReleaseContext
    GetLastError
    Printer friendly API declarations
    My comment:
    Transact-SQL HASHBYTES() function computes MD5 and SHA1 hashes identical to those produced by VFP and C# code samples above.



    * * *
    One-way hash functions can be used for creating a fingerprint for a block of data.

    Also hash functions can be used to evaluate passwords. In Users table of your FoxPro application you store not passwords but their hash values.

    It is extremely difficult, if ever possible, to find the original string for a given hash value -- depends on the hash algorithm as well as computer power and methodology you have.

    * * *
    Message Digest: The representation of text in the form of a single string of digits, created using a formula called a one-way hash function.

    One-Way Hash Function: An algorithm that turns messages or text into a fixed string of digits, usually for security or data management purposes. The "one way" means that it is nearly impossible to derive the original text from the string.

    Hash Collision: More than one input message producing identical hash output.

    * * *
    Secure Hash Algorithm, a hash function developed by the NSA for use with NIST Digital Signature Standard (DSS). NSA almost immediately developed a minor change known as SHA-1. Both SHA and SHA-1 produce a 160-bit digest. SHA-1 is used in SSL.

    * * *
    MD-5 is a one-way message-digest hash function. The algorithm processes input text and creates a 128-bit message digest which is unique to the message and can be used to verify data integrity.

    MD-5 was developed by Ron Rivest and is intended to be used in digital signatures applications. Earlier message digest algorithms include obsolete MD-2 and MD-4.

    See also:
  • RFC 1321 - The MD5 Message-Digest Algorithm
  • What are MD2, MD4, and MD5?
  • Example C Program: Creating an MD-5 Hash From File Content.
  • MD5 Online Cracking using Rainbow Tables
  • RFC 3174 - US Secure Hash Algorithm 1 (SHA1)
  • More on Newly Broken SHA1 on Alex Feldstein"s blog
  • Hash Collisions Q&A
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    User Contributed Notes:
    Malcolm Greene | 2005-04-06 00:16:27
    Are there any Windows version (or service pack) dependencies with this code (advapi32.dll)? I've been burned trying to get the FFC _Crypto class to work across different versions of Windows, re: different flavors of rsaenh.dll. (I noticed that rsaenh.dll is not referenced in above code, but I'm still concerned about the same problem version dependencies).

    Thoughts?
    Malcolm

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