xtea.h : XTEA (eXtended Tiny Encryption Algorithm)
[/protocol : Collection of protocol related modules]

Block cipher encryption/decryption algorithm. More...

Functions
void	xtea_init (const u32_t key[4])
	Initialise 128-bit key for encryption/decryption.
void	xtea_encrypt (u32_t data[2])
	Encrypt 64-bit data with 128-bit key.
void	xtea_decrypt (u32_t data[2])
	Decrypt 64-bit data with 128-bit key.

---

Detailed Description

Files: xtea.h & xtea.c

See also:

http://en.wikipedia.org/wiki/XTEA

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Function Documentation

void xtea_init

(

const u32_t

key[4]

)

Parameters:

key

4 x 32-bit values

Definition at line 64 of file xtea.c.

{
    u8_t i;

    for(i=0;i<4;i++)
    {
        xtea_key[i] = key[i];
    }
}

void xtea_encrypt

(

u32_t

data[2]

)

Parameters:

data

2 x 32-bit values

Definition at line 74 of file xtea.c.

{
    u8_t i;

    u32_t d0  = data[0];
    u32_t d1  = data[1];
    u32_t sum = 0;

    for (i=XTEA_NUMBER_OF_ROUNDS; i != 0; i--)
    {
        d0  += (((d1 << 4) ^ (d1 >> 5)) + d1) ^ (sum + xtea_key[sum & 3]);
        sum += XTEA_DELTA;
        d1  += (((d0 << 4) ^ (d0 >> 5)) + d0) ^ (sum + xtea_key[(sum>>11) & 3]);
    }
    data[0] = d0;
    data[1] = d1;
}

void xtea_decrypt

(

u32_t

data[2]

)

Parameters:

data

2 x 32-bit values

Definition at line 92 of file xtea.c.

{
    u8_t i;

    u32_t d0  = data[0];
    u32_t d1  = data[1];
    u32_t sum = XTEA_DELTA*XTEA_NUMBER_OF_ROUNDS;

    for (i=XTEA_NUMBER_OF_ROUNDS; i != 0; i--)
    {
        d1  -= (((d0 << 4) ^ (d0 >> 5)) + d0) ^ (sum + xtea_key[(sum>>11) & 3]);
        sum -= XTEA_DELTA;
        d0  -= (((d1 << 4) ^ (d1 >> 5)) + d1) ^ (sum + xtea_key[sum & 3]);
    }
    data[0] = d0;
    data[1] = d1;
}