private uint[] sjclDecryptAes()
{
int L;
int ivl = this.sjclBitLength(this.uint32IV) / 8;
int ol = this.ctBitLength;
uint[] outX = this.uint32Out;
uint[] tag = this.uint32Tag;
ol = (ol - this.tagSize) / 8;//out length (byte)
if (ivl < 7)
{
throw new Exception("IV must be at least 7 bytes");
}
// compute the length of the length
uint olx = (uint)ol;
for (L = 2; L < 4 && (olx >> 8 * L) != 0; L++)
{
}
if (L < 15 - ivl)
{
L = 15 - ivl;
}
long[] ivx = this.sjclClampForIV(this.uint32IV, 8 * (15 - L));
// decrypt
SJCLResult ret = this.sjclCCMCounterMode(outX, ivx, tag, L);
// check the tag
uint[] tag2 = this.sjclCCMComputeTag(ret.Data, ivx, L);
if (this.sjclEqual(ret.Tag, tag2) == false)
{
throw new Exception("tag doesn't match");
}
return(ret.Data);
}
private SJCLResult sjclCCMCounterMode(uint[] aOut, long[] aIV, uint[] aTag, int aL)
{
int bl = this.ctBitLength - this.tagSize;//original data size
int l = aOut.Length;
// start the ctr
long partial = this.sjclPartialLong(8, (uint)(aL - 1), 0);
long[] partialAr = new long[] { partial }; //one object array
uint[] temp1 = this.sjclConcat(partialAr, aIV);
uint[] temp2 = new uint[3]; //{0,0,0}
uint[] tempMerge = new uint[temp1.Length + temp2.Length];
Array.Copy(temp1, 0, tempMerge, 0, temp1.Length);
Array.Copy(temp2, 0, tempMerge, temp1.Length, temp2.Length);//merge
uint[] ctr = new uint[4];
Array.Copy(tempMerge, 0, ctr, 0, ctr.Length);
// en/decrypt the tag
uint[] cryptCtr = this.sjclCrypt(ctr, false);
uint[] tag = this.sjclXOR4(aTag, cryptCtr);
// en/decrypt the data
if (l == 0)
{//data size is 0
return(new SJCLResult(tag, new uint[0]));
}
uint[] enc;
uint[] aoutx = new uint[aOut.Length + 3];
Array.Copy(aOut, 0, aoutx, 0, aOut.Length);//extend
for (int i = 0; i < l; i += 4)
{
ctr[3]++;
enc = this.sjclCrypt(ctr, false);
aoutx[i] ^= enc[0];
aoutx[i + 1] ^= enc[1];
aoutx[i + 2] ^= enc[2];
aoutx[i + 3] ^= enc[3];
}
SJCLResult ret = new SJCLResult(tag, this.sjclClamp(aoutx, bl));
return(ret);
}
