Confidentiality (Privacy) - Libelium Waspmote v15 and Plug & Sense Programming Manual

4. Confidentiality (privacy)

Confidentiality refers to ensure that information is not accessed by unauthorized people. Information is intelligible only to its
rightful recipients. Although third parties may be able to read (a copy of ) the message sent, they must not be able to make sense
of it. Confidentiality is assurance of data privacy. Sending frames with confidentiality can be achieved through symmetric key
encryption. AES algorithm has been implemented for this purpose.
Advanced Encryption Standard (AES) is a symmetric key encryption algorithm that supports key lengths of 128, 192, and 256
bits. AES encrypts a block of bytes at the same time, unlike stream ciphers that encode each single item individually. This feature
allows the algorithm to be very fast. It has the advantage of occupying very little memory and consequently makes it very
suitable for low memory capacity devices.
AES is able to encrypt and decrypt a block of data using an AES key. The key and the block of data have a fixed length. The
length of the block of data is always 128-bit (16 bytes), while the key size can be:
• 128-bit key size (16 bytes)
192-bit key size (24 bytes)
•
256-bit key size (32 bytes)
•
As AES is classified as a block cipher algorithm, there are different modes of operation. A mode of operation describes how
to repeatedly apply a cipher's single-block operation to securely transform amounts of data larger than a block. This library
implements two modes of operation:
ECB mode: The simplest of the encryption modes is the electronic codebook (ECB) mode. The message is divided into
•
blocks of 16 bytes and each block is encrypted separately. Notice that this mode is the only one supported by Meshlium.
Figure : CBC mode encryption
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Confidentiality (privacy)
v7.0