I'm having some difficulties implementing the AES encryption primitives for an msp430fr5969 micro controller following the indications described here:
www.ti.com.cn/.../slau367f.pdf
more particularly the AES CBC cipher mode:
www.ti.com.cn/.../slau367f.pdf
My current implementation looks like:
int i = 8, j = 0;
uint16_t *tmp;
// key is given in 16-bit words
uint16_t key[] = { 0x1234, 0x5678, 0x9ABC, 0xDEF0,
0xDEF1, 0xDEF2, 0xDEF3, 0xDEF4};
uint16_t iv[] = { 0x7545, 0xA546, 0x5461, 0x7526,
0xDCD1, 0x21A2, 0xD453, 0x216F};
// AESOPx prepares the accelerator for encryption
// Reset AES controller state o 0x0. AESACTL0 is
// the control register
AESACTL0 |= AESSWRST;
// Prepare for encryption
AESACTL0 |= AESCMEN;
AESACTL0 &= ~AESOP0;
AESACTL0 &= ~AESOP1;
// Load the key
while(i--)
AESAKEY = (uint16_t)key[j++];
// Wait for the AES accelerator to finish
while(AESASTAT & AESBUSY);
// Load initialization vector(needed for CBC)
i = 8; j = 0;
while(i--)
AESAXIN = (uint16_t)iv[j++];
// Wait for the AES accelerator to finish
while(AESASTAT & AESBUSY);
// Setup DMA as described in the manual
// Channel selection. AES trigger 0 on channel 0 ------------------
DMACTL0 = DMA0TSEL_11;
// The AES accelerator makes use of level sensitive triggers
DMA0CTL |= DMALEVEL;
// Set transfer mode. For the AES accelerator it is always single transfer mode (DMADTx = 000)
DMA0CTL |= DMADT_0;
// Enable DMA
//DMA0CTL |= DMAEN;
// Source address
DMA0SAL = (uint16_t)&AESADOUT;
// Destination address. The cipher text is a byte array(char*)
tmp = (uint16_t*)cipher_text;
DMA0DAL = (uint16_t)tmp;
// Size in words
DMA0SZ = (uint16_t)number_of_blocks * 8;
// Set increment value(2 bytes/ 1 word)
// Increment source address
DMA0CTL |= DMASRCINCR_3;
// Increment destination address
DMA0CTL |= DMADSTINCR_3;
// Channel selection. AES trigger 1 on channel 1 ------------------
DMACTL0 = DMA1TSEL_12;
// The AES accelerator makes use of level sensitive triggers
DMA1CTL |= DMALEVEL;
// Set transfer mode. For the AES accelerator it is always single transfer mode (DMADTx = 000)
DMA1CTL |= DMADT_0;
// Enable DMA
DMA1CTL |= DMAEN;
// Source address
// Destination address. The plain text is a byte array(char*)
tmp = (uint16_t*)plain_text;
DMA1DAL = (uint16_t)tmp;
// Destination address
DMA1DAL = (uint16_t)&AESAXDIN;
// Size in words
DMA1SZ = (uint16_t)n_blocks * 8;
// Set increment value(2 bytes/ 1 word)
// Increment source address
DMA1CTL |= DMASRCINCR_3;
// Increment destination address
DMA1CTL |= DMADSTINCR_3;
// According to the manual setting the number of blocks should trigger the
// the encryption but it doesn't
AESACTL1 &= ~AESBLKCNT0;
AESACTL1 |= AESBLKCNT1;
// Wait for the AES accelerator to finish
while(AESASTAT & AESBUSY);
// Wait for dma transfers to finish
while (!(DMA0CTL & DMAIFG));
while (!(DMA1CTL & DMAIFG));
Why isn't encryption triggered upon setting the number of blocks?
