Generate digest

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4D v20.1

Generate digest


Generate digest ( param ; algorithm {; *} ) -> Function result

Parameter	Type	Description
param	BLOB, Text variable	Blob or text for which to get digest key
algorithm	Longint	Algorithm used to return key: 0 = MD5 Digest, 1 = SHA1 Digest, 2 = 4D digest, 3 = SHA-256 digest, 4 = SHA-512 digest
*	Operator	Encode digest in Base64URL
Function result	Text	Value of digest key

Description

The Generate digest command returns the digest key of a BLOB or text after application of an encryption algorithm.

Pass a Text or BLOB field or variable in the param parameter. The Generate digest function returns the digest key as a string.

In the algorithm parameter, pass a value designating which hash function to use. Use one of the following constants, found in the Digest Type theme:

Constant	Value	Comment
4D REST digest	2	Internal algorithm of 4D, useful in the context of the On REST Authentication database method when you want to use your own list of users.
MD5 digest	0	Message Digest 5 algorithm. A series of 128 bits returned as a string of 32 hexadecimal characters.
SHA1 digest	1	Secure Hash 1 algorithm. A series of 160 bits returned as a string of 40 hexadecimal characters.
SHA256 digest	3	(SHA-2 family) SHA-256 is a series of 256 bits returned as a string of 64 hexadecimal characters.
SHA512 digest	4	(SHA-2 family) SHA-512 is a series of 512 bits returned as a string of 128 hexadecimal characters.

Note: It is not recommended to use MD5 and SHA algorithms to handle passwords; if you need to check passwords, you are advised to use Generate password hash and Verify password hash commands.

By default if the * parameter is omitted, the returned digest is encoded in hexadecimal. Pass the * parameter if you want it to be encoded in Base64URL.

The value returned for the same object is the same on all the platforms (macOS/Windows). The calculation is performed based on the representation in UTF-8 of the text passed in the parameter.

Note: If you use the command with an empty text/BLOB, it does not return void but a string value (for example "d41d8cd98f00b204e9800998ecf8427e" for MD5).

Example 1

This example compares two images using the MD5 algorithm:

 C_PICTURE($vPict1;$vPict2)

 C_BLOB($FirstBlob;$SecondBlob)

 READ PICTURE FILE("c:\\myPhotos\\photo1.png")

 If(OK=1)

    READ PICTURE FILE("c:\\myPhotos\\photo2.png")

    If(OK=1)

       PICTURE TO BLOB($vPict1;$FirstBlob;".png")

       PICTURE TO BLOB($vPict2;$SecondBlob;".png")

 

       $MD5_1:=Generate digest($FirstBlob;MD5 digest)

       $MD5_2:=Generate digest($SecondBlob;MD5 digest)

 

       If($MD5_1#$MD5_2)

          ALERT("These two images are different.")

       Else

          ALERT("These two images are identical.")

       End if

    End if

 End if

Example 2

These examples illustrate how to retrieve the digest key of a text:

 $key1:=Generate digest("The quick brown fox jumps over the lazy dog.";MD5 digest)

  // $key1 is "e4d909c290d0fb1ca068ffaddf22cbd0"

 $key2:=Generate digest("The quick brown fox jumps over the lazy dog.";SHA1 digest)

  // $key2 is "408d94384216f890ff7a0c3528e8bed1e0b01621"

Example 3

This example only accepts the "admin" user with the password "123" that does not match a 4D user:

  //On REST Authentication database method

 C_TEXT($1;$2)

 C_BOOLEAN($0;$3)

  //$1: user

  //$2: password

  //$3: digest mode

 If($1="admin")

    If($3)

       $0:=($2=Generate digest("123";4D digest))

    Else

       $0:=($2="123")

    End if

 Else

    $0:=False

 End if