int size = 256;
byte[] src1 = new byte[size];
byte[] src2 = new byte[size];
byte[] src3 = new byte[size];
int i;
for (i = 0; i < size; i++) {
src1[i] = (byte)i;
src2[i] = (byte)i;
src3[i] = (byte)(size - i - 1);
}
Mac m = Mac.getInstance(algName);
byte[] b = {(byte)0, (byte)0, (byte)0, (byte)0, (byte)0};
SecretKeySpec sks = new SecretKeySpec(b, "SHA1");
m.init(sks);
byte[] res = m.doFinal(src1);
String sign1 = new String(res);
m.init(sks);
res = m.doFinal(src2);
String sign2 = new String(res);
m.init(sks);
res = m.doFinal(src3);
String sign3 = new String(res);
if (sign1.compareTo(sign2) != 0 || sign1.compareTo(sign3) == 0 ||
sign2.compareTo(sign3) == 0) {
throw new Exception ("Signature is not correct for algorithm " + algName);
}
