All cryptographic data are handled following the big-endian format (AES standard). That means that the first byte (lowest address) of the data is the Most Significant Byte (MSB).
The APB bus uses little endian format. That means that the Least Significant Byte (LSB) is stored at the lowest address.
For example, a 128-bit block D[A] = 0x00112233445566778899AABBCCDDEEFF stored at address A (multiple of 4) appears on APB bus as the following 32-bit words:
- D[A+0] = 0x33221100
- D[A+4] = 0x77665544
- D[A+8] = 0xBBAA9988
- D[A+12] = 0xFFDDEEC