int AES_init()

in src/aes.c [308:365]

• 46 lines of code
• 18 McCabe index (conditional complexity)

int AES_init(amcl_aes* a,int mode,int nk,char *key,const char *iv)
{
    /* Key length Nk=16, 24 or 32 bytes */
    /* Key Scheduler. Create expanded encryption key */
    int i;
    int j;
    int k;
    int N;
    int nr;
    unsign32 CipherKey[8];

    nk/=4;

    if (nk!=4 && nk!=6 && nk!=8) return 0;

    nr=6+nk;

    a->Nk=nk;
    a->Nr=nr;

    AES_reset(a,mode,iv);

    N=NB*(nr+1);

    for (i=j=0; i<nk; i++,j+=4)
    {
        CipherKey[i]=pack((uchar *)&key[j]);
        a->fkey[i]=CipherKey[i];
    }
    for (j=nk,k=0; j<N; j+=nk,k++)
    {
        a->fkey[j]=a->fkey[j-nk]^SubByte(ROTL24(a->fkey[j-1]))^rco[k];
        if (nk<=6)
        {
            for (i=1; i<nk && (i+j)<N; i++)
                a->fkey[i+j]=a->fkey[i+j-nk]^a->fkey[i+j-1];
        }
        else
        {
            for (i=1; i<4 && (i+j)<N; i++)
                a->fkey[i+j]=a->fkey[i+j-nk]^a->fkey[i+j-1];
            if ((j+4)<N) a->fkey[j+4]=a->fkey[j+4-nk]^SubByte(a->fkey[j+3]);
            for (i=5; i<nk && (i+j)<N; i++)
                a->fkey[i+j]=a->fkey[i+j-nk]^a->fkey[i+j-1];
        }

    }
    /* now for the expanded decrypt key in reverse order */

    for (j=0; j<NB; j++) a->rkey[j+N-NB]=a->fkey[j];
    for (i=NB; i<N-NB; i+=NB)
    {
        k=N-NB-i;
        for (j=0; j<NB; j++) a->rkey[k+j]=InvMixCol(a->fkey[i+j]);
    }
    for (j=N-NB; j<N; j++) a->rkey[j-N+NB]=a->fkey[j];
    return 1;
}