#Mvp excel vba tutorial how to#
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The top function, Hash, the one that creates a Base64 encoded hash value from a passed text, contains less than a handful of code lines: To conclude: For only a little overhead, the hash values can be treated as normal plain text.ДЄ set of functions is used to create hash values:

#Mvp excel vba tutorial portable#

It offers the same - a printable and portable string of ASCII characters - but consumes only 50% or less additional space then the byte count: The simple method would be to convert to the hexadecimal representation of the bytes, for example four bytes (here character is the third):Д«ut that consumes twice as many characters, thus a SHA256 hash would have a length of 64 characters - not very efficient.ДЄ better method is to use Base64 encoding. As these bytes can take many other values than those for normal ASCII characters - even control characters and other non-printable characters - the byte array must for many practical purposes be converted to something printable. Note, that the lengths listed above for the hash algorithms are the lengths of the generated byte arrays. For higher demands, use SHA512 or SHA384, but be aware, that SHA384 is not supported in all environments. While MD5 and SHA1 can be well suited for some purposes, the general consensus is, that SHA256 is the minimum method to use for hashing passwords. The algorithms supported and their byte lengths are: The expected hash value of the file is listed, and this must match the calculated hash value of the actual downloaded file.

#Mvp excel vba tutorial verification#

For example, SHA1, and even the very old MD5, are often used when downloading files for verification of the integrity of the downloaded file. These have evolved over time, and the oldest - also producing the shortest hash values - are now deprecated, though still widely used for less demanding purposes. The mathematical method used to hash a string is called an algorithm.

If these values match, the password is accepted.

To verify the password, its hash value is generated and compared with the stored hash value. Instead of storing the password, the hash value is stored. The typical usage of hash values is for 'storing' users' passwords. The point is to be able to create a code based on an input, (later) to recreate that code, and then to check if the later code matches the first if it does, the later input is assumed to match the original input. Note, that the code is not unique as, in theory, the same code could be generated from different inputs, though - due to the extreme count of combinations for a given string length - this is unlikely to happen in real life. Hashing, in this context, is the process of creating a non-reversible fixed length code that identifies the input.

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The last demonstrates how to save and verify passwords totally safe using these tools. The three first deal, as stated, with hashing and encrypting/decrypting based on the CNG API, while the forth explains how to combine these techniques with the little known feature of Access, storing binary data, as this in many cases will represent the optimal storage method for hashed or encrypted data.

Storing passwords in VBA using the Microsoft NG Cryptography (CNG) API.

Using binary storage to serve the Microsoft NG Cryptography (CNG) API.

Encryption in VBA using the Microsoft NG Cryptography (CNG) API.

Hashing in VBA using the Microsoft NG Cryptography (CNG) API.

Utilise Microsoft's Next Generation Cryptography (CNG) API in VBA.

This allows you to skip parts you are either familiar with or wish to implement later if at all.

A search with Bing or Google will return a long list of resources to study. The theory for and the clever mathematics behind hashing and encryption will not be touched this is covered massively in books and articles published over a long period of time by dedicated experts. This series details one method to implement these features in applications supported by VBA (Visual Basic for Applications), for example Microsoft Access and Microsoft Excel. The Microsoft CNG APIs constitute a collection of more than a dozen APIs that handle all the aspects and supporting functions to calculate hash values and perform encryption and decryption meeting modern high demands and standards.