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2013-02-15T19:12:46Z

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2013-02-06T22:36:41Z

Created page with "= Action = This statement of function uses the Xmega AES encryption engine to decrypt a block of data. ..."

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== (**COPIED FROM ENGLISH PAGE**) === Action =

This statement of function uses the Xmega AES encryption engine to decrypt a block of data.

 

 

= Syntax =

AESDECRYPT  key, var , size

targ = AESDECRYPT ( key, var , size)

 

 

= Remarks =
<div style="padding: 0px; margin: 0px 0px 0px 4px;">
{| width="604" cellspacing="0" cellpadding="1" border="1" style="border: 2px solid rgb(0, 0, 0); border-spacing: 0px; border-collapse: collapse;"
|- style="vertical-align: top;"
| valign="top" width="14%" style="width: 81px; border: 1px solid rgb(0, 0, 0);" |
key

| valign="top" width="100%" style="width: 514px; border: 1px solid rgb(0, 0, 0);" |
The name of a label that contains 16 bytes of key data. Or an array holding 16 bytes of key data.

|- style="vertical-align: top;"
| valign="top" width="14%" style="width: 81px; border: 1px solid rgb(0, 0, 0);" |
var

| valign="top" width="100%" style="width: 514px; border: 1px solid rgb(0, 0, 0);" |
A variable or array containing the data to be encrypted. When you use the statement, this variable will contains the encrypted data after the conversion.

|- style="vertical-align: top;"
| valign="top" width="14%" style="width: 81px; border: 1px solid rgb(0, 0, 0);" |
size

| valign="top" width="100%" style="width: 514px; border: 1px solid rgb(0, 0, 0);" |
The number of bytes to encrypt. Encryption is done with blocks of 16 bytes. So the size should be a multiple of 16. If you supply only 14 bytes this is ok too, but the result will still be 16 bytes.

[[File:Notice.jpg|left|Notice.jpg]]It is important that your array is big enough to hold the result.

Without the full 16 byte result, you can not decrypt the data.

|- style="vertical-align: top;"
| valign="top" width="14%" style="width: 81px; border: 1px solid rgb(0, 0, 0);" |
targ

| valign="top" width="100%" style="width: 514px; border: 1px solid rgb(0, 0, 0);" |
In case you use the function, this variable will hold the result.

|}
</div>
 

This function only works for Xmega chips that have an AES encryption unit.

128 bit encryption is used.

 

You can either use a label with a fixed key, or use a variable.

You should use the same key data for encryption and decryption.

 

 

 

= See also =

[[AESENCRYPT]]

 

 

= Example =

 <source lang="bascomavr">
'----------------------------------------------------------------
' (c) 1995-2010, MCS
' xm128-AES.bas
' This sample demonstrates the Xmega128A1 AES encryption/decryption
'-----------------------------------------------------------------

$regfile = "xm128a1def.dat"
$crystal = 32000000
$hwstack = 64
$swstack = 40
$framesize = 40

'include the following lib and code, the routines will be replaced since they are a workaround
$lib "xmega.lib"
$external _xmegafix_clear
$external _xmegafix_rol_r1014

'first enable the osc of your choice
Config Osc = Enabled , 32mhzosc = Enabled

'configure the systemclock
Config Sysclock = 32mhz , Prescalea = 1 , Prescalebc = 1_1

Config Com1 = 38400 , Mode = Asynchroneous , Parity = None , Stopbits = 1 , Databits = 8

'$external _aes_enc

Dim Key(16) As Byte ' room for key
Dim Ar(34) As Byte
Dim Arenc(34) As Byte
Dim J As Byte
Print "AES test"

Restore Keydata
For J = 1 To 16 ' load a key to memory
Read Key(j)
Next

'load some data
For J = 1 To 32 ' fill some data to encrypt
Ar(j) = J
Next

Aesencrypt Keydata , Ar(1) , 32
Print "Encrypted data"
For J = 1 To 32 ' fill some data to encrypt
Print Ar(j)
Next

Aesdecrypt Keydata , Ar(1) , 32
Print "Decrypted data"
For J = 1 To 32 ' fill some data to encrypt
Print Ar(j)
Next

Print "Encrypt function"
Arenc(1) = Aesencrypt(keydata , Ar(1) , 32)
For J = 1 To 32 ' fill some data to encrypt
Print Ar(j) ; "-" ; Arenc(j)
Next

Print "Decrypt function"
Ar(1) = Aesdecrypt(keydata , Arenc(1) , 32)

For J = 1 To 32
Print J ; ">" ; Ar(j) ; "-" ; Arenc(j)
Next

End

Keydata:
Data 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16
</source> {{Languages}}

[[Category:BASCOM_Language_Reference/de]]

AESDECRYPT/de - Revision history

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Admin: Created page with "= Action = This statement of function uses the Xmega AES encryption engine to decrypt a block of data. ..."