testbyt | Command line and GUI tools | Plugin library

Shouldn't it be in your code assert testbytes == plaintext to test your hypothesis?

Anyway. An encryption consists of two parts, the algorithm (here AES) and the mode of operation (here ECB). The algorithm itself can only encrypt a single block. The mode of operation extends this to plaintexts of any length. So that your assumption is correct, the individual processing steps and their order for decryption and encryption must be identical for both parts, algorithm and mode of operation.

Concerning the ECB mode your assumption is true, because each block is processed independently from the other (which also makes this mode insecure). However, for AES your assumption is not true, since decryption is essentially done in the reverse order to encryption, for details see here.

The easiest way to check the latter is to encrypt only one block without padding. Since the ECB mode does not use an IV, the encryption is reduced to the AES primitive itself. Padding does not have to be disabled, because PyCryptodome does not implicitly pad (in contrast to many other libraries). This case just corresponds to your code (although you have to check the equality between testbytes and plaintext). The result verifies that a double encryption using AES does not result in the original plaintext.

In your Vapor code you decode the file and then extract only the array to a property so assuming that this is what you encode and send to the client then you only receive the array.

Like this

It seems like the byte[] being passed is a different array. They may have equal values, but be different references.

There's no way of acquiring a Span over an arbitrary struct without unsafe, since such a span would allow you to change any bit of the struct in any way, possibly violating the type's invariants - that's inherently an unsafe operation.

Okay, but what about ReadOnlySpan? Notice that you had to put the StructLayoutAttribute on your struct for your code to be sensible. That should be a hint. Imagine trying to write an even simpler method, one that returns a byte[] for any arbitrary T where T : struct. You have to find out the size of the struct first, don't you? Well, how do you find out the size of a struct in C#? You can either use the sizeof operator, which requires an unsafe context and needs the struct to be an unmanaged type; or you can Marshall.SizeOf which is wonky and works only on structs with sequential or explicit byte layout. There's no safe, general way, thus you cannot do that.

The Span and ReadOnlySpan weren't designed with accessing struct bytes in mind, but rather with spanning fragments of arrays, which have a known size and are guaranteed to be sequential.

If you are confident that you know what you're doing, you can do that in an unsafe context - that's what it's for. But note that your solution with unsafe doesn't generalise to arbitrary structs, for the reasons noted above.

If you intend your struct to be used as a buffer for IO operations, you might want to look into fixed size buffers. They also require an unsafe context, but you can encapsulate the unsafeness inside your struct and return a Span to that fixed buffer. Basically anything that tackles the byte structure of objects in memory requires unsafe in .NET, as memory management is the thing that this "safety" refers to.

The default marshaling behavior for System.Boolean is as a 4 byte integer in accordance with the Microsoft/Windows API definition of BOOL. So Marshal.PtrToStructure assumes that the unmanaged representation of TestStruct is 24 bytes large with the first 4 bytes being taken up by TestStruct.Valid, which throws off Value1 and the other fields.

You can change this behavior by applying the [MarshalAs(UnmanagedType.I1)] attribute to the bool field.

There is problem MultiIndex in columns.

Solution is change:

There was a double problem there:

• The connection to the console via PUTTY needed to configure UTF8 for the console.
• Files must be in UTF8 format (there were in ISO)

Thanks a lot.

delete []-ing something which isn't new []-ed, nor you own, is severely contra-indicated.

Look at these lines:

Yes BigEndian works much better