Android Question How to implement a XOR between array of bytes

[prbmjr]

Hi everyone,

I must implement a XOR operation between arrays of bytes, because I need to implement a special data encryption requeted by my client..

I found only the bit.xor function between integers, Is there a way to implement a XOR with arrays?

Thank you in advance!

br,

Paulo Bueno

 

[prbmjr]

For reference, it would be a function like numpy.bitwise_xor (python) - https://numpy.org/doc/stable/refere....html?highlight=bitwise_xor#numpy.bitwise_xor

 

[Erel]

Sub ArrayXor (b1() As Byte, b2() As Byte) As Byte()
    'assuming that the arrays are with the same length
    Dim b3(b1.Length) As Byte
    For i = 0 To b1.Length - 1
        b3(i) = Bit.Xor(b1(i), b2(i))
    Next
    Return b3
End Sub

 

[prbmjr]

Sub ArrayXor (b1() As Byte, b2() As Byte) As Byte()
    'assuming that the arrays are with the same length
    Dim b3(b1.Length) As Byte
    For i = 0 To b1.Length - 1
        b3(i) = Bit.Xor(b1(i), b2(i))
    Next
    Return b3
End Sub

Hi Erel,

Thank you very much for your answer. I had something like this already implemented, but my concern is about the performance, if I have to use this type of code instead a real function/library using big arrays, like 500k, 50mb, etc... These arrays are entires files that must be encrypted... I have a similar code in python for reference and this runs really fast using the function numpy.bitwise_xor . I will try and I let you know with the result.

br,

Paulo Bueno

 

[Erel]

Test it.

Dim b1(500000), b2(500000) As Byte
For i = 1 To 100
    Dim n As Long = DateTime.Now
    ArrayXor(b1, b2)
    Log(DateTime.Now - n)
Next

On my device it takes between 0 to 1 millisecond.

 

[prbmjr]

Test it.

Dim b1(500000), b2(500000) As Byte
For i = 1 To 100
    Dim n As Long = DateTime.Now
    ArrayXor(b1, b2)
    Log(DateTime.Now - n)
Next

On my device it takes between 0 to 1 millisecond.

Hi Erel,

I tested with this code:

Sub ArrayXor_teste As Byte()
    'assuming that the arrays are with the same length
    Dim b1(552643), b2(552643) As Byte
    Dim b3(b1.Length) As Byte

    For i = 0 To b1.Length - 1
        
        b3(i) = Bit.Xor(b1(i), b2(i))
    Next
    Return b3
End Sub

In my test I used a Sansung S8 device and takes 32 seg, why??

 

[DonManfred]

In my test I used a Sansung S8 device and takes 32 seg, why??

Did you tested it in RELEASE mode?? NEVER do performance measures in DEBUG mode.

 

[prbmjr]

Did you tested it in RELEASE mode?? NEVER do performance messures in DEBUG mode.

Hi,

No, In debug mode, I will test in release mode now...

Thank you!

 

[DonManfred]

i did a quick test in one app of mine.
As the app does other things in parallel too i got 135ms as result. Still FAST; 0,135 Seconds.

 

[prbmjr]

i did a quick test in one app of mine.
As the app does other things in parallel too i got 135ms as result. Still FAST; 0,135 Seconds.

Hi,

I tested in release mode and all process is quite fast now..