Admin at 22:19, 12 December 2014

2014-12-12T22:19:53Z

Admin: Created page with "= Action = Encrypts a variable or array using the XTEA protocol.
2013-02-12T19:25:29Z

Created page with "= Action = Encrypts a variable or array using the XTEA protocol. Action =

Encrypts a variable or array using the XTEA protocol.

 

 

= Syntax =

XTEAENCODE  Msg , Key , size

 

 

= Remarks =
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Msg

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The variable to encrypt. Encryption is performed in blocks of 8 bytes. This means that you need to specify an array that has a minimal size of 8 bytes. For example, 2 Longs will be 8 bytes in size.

 

After the encryption is performed, Msg will contain the encrypted data.

The original data will be overwritten.

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Key

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The 128 bit key which is used to encrypt the message data.

You need to pass this as an array of 8 bytes.

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Size

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The number of bytes to encrypt. This must be a multiple of 8.

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The XTEA encryption/decryption is described well at [http://en.wikipedia.org/wiki/XTEA http://en.wikipedia.org/wiki/XTEA]

The XTEA is an enhanced version of the TEA encryption protocol.

 

The XTEA encoding/decoding routines have a small footprint. You could use the XTEADECODE in a bootloader and encrypt your firmware.

 

 

= See also =

[[XTEADECODE]]

 

 

= Example =

 <source lang="bascomavr">
'----------------------------------------------------------
' XTEA.BAS
' This sample demonstrates the XTEA encryption/decryption
' statements
' (c) 1995-2011 MCS Electronics
'----------------------------------------------------------
$regfile = "m88def.dat"
$hwstack = 40
$swstack = 32

'The XTEA encryption/decryption has a small footprint
'XTEA processes data in blocks of 8 bytes. So the minimum length of the data is 8 bytes.
'A 128 bit key is used to encrypt/decrypt the data. You need to supply this in an array of 8 bytes.

'Using the encoding on a string can cause problems when the data contains a 0. This is the end of the string marker.

Dim Key(16) As Byte '128 bit key
Dim Msg(32) As Byte ' this need to be a multiple of 8

Dim B As Byte ' counter byte

For B = 1 To 16 ' create a simple key and also fill the data
Key(b) = B
Msg(b) = B
Next

Xteaencode Msg(1) , Key(1) , 32 ' encode the data

For B = 1 To 16
Print Hex(msg(b)) ; " , " ;
Next
Print

Xteadecode Msg(1) , Key(1) , 32 ' decode the data

For B = 1 To 16
Print Hex(msg(b)) ; " , " ;
Next 'it should print 1-16 now
Print

End
</source> {{Languages}}

[[Category:BASCOM Language Reference]]

@@ Line 38: / Line 38: @@
 The 128 bit key which is used to encrypt the message data.
-You need to pass this as an array of 8 bytes.
+You need to pass this as an array of 16 bytes.
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