Question 1

Should I use Tiny AES C or OpenSSL for my IoT device?

Accepted Answer

Use Tiny AES C if your device has severe memory constraints and you need a minimal footprint; OpenSSL is better for performance and features but is much larger. Tiny AES is ideal for microcontrollers, while OpenSSL suits servers or high-speed applications.

Question 2

How to implement PKCS7 padding with Tiny AES CBC mode?

Accepted Answer

You need to add padding manually before encryption and remove it after decryption. For example, pad data to a multiple of 16 bytes using PKCS7, then call AES_CBC_encrypt_buffer. The README recommends PKCS7 but doesn't provide it, so you must code it yourself.

Question 3

Is Tiny AES C secure for production use?

Accepted Answer

It's verified against NIST test vectors for algorithm correctness, but lacks runtime error checking and padding, so you must handle input validation and padding externally. For critical systems, consider supplementing with additional security measures.

Question 4

How to compile Tiny AES for an ARM microcontroller?

Accepted Answer

Include aes.h, define modes like CBC or CTR via compiler flags (e.g., -DCTR=1), and compile with ARM GCC as shown in the README examples. Adjust flags for your specific toolchain and platform requirements.

Question 5

Does Tiny AES support AES-256?

Accepted Answer

Yes, you can enable AES-256 by defining the symbol AES256 in aes.h. By default, it uses 128-bit keys, but larger key sizes are supported with minimal increase in code size.

Question 6

What are the memory requirements for Tiny AES?

Accepted Answer

It uses less than 200 bytes of RAM and 1-2K of ROM on ARM, depending on enabled modes. For instance, with only CTR mode, code size can be under 1KB, as detailed in the README's GCC size output.

tiny-AES128-C

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