Byte Swapping Options - Samsung S5PC110 Manual

S5PC110_UM 2 ADVANCED CRYPTO ENGINE

2.2.3 BYTE SWAPPING OPTIONS

SSS supports byte-swapping options for various data. Byte swapping in this context means byte order reversion in
a 32-bit word boundary.
Figure 2-8 AES Byte Swapping Scheme
According to 2-8, AES has five swapping options for every data (be it data input, data output, initial value,
Figure
key, and counter).
Moreover, all DMA (BRDMA and BTDMA) have their own swapping option. The byte-swapping option of DMA
should follow the bus endian.
1. For little endian bus, the DMA should swap data.
2. For big endian bus, the DMA should not swap data.
The only reason why option 2 must be used is that S5PC110 supports little endian case.
In case DES, Hash, and PKA contain different numbers of data, the same scheme will be applied.
2-8