kvJbhvxy

1package me.academeg.SplitSecretChina;
2
3@SuppressWarnings("unused")
4public class SplitSecretChinaDecode {
5
6    private int[] publicKey;
7    private int[] secretKey;
8    private int countSecret;
9
10    public SplitSecretChinaDecode(int[] publicKey, int[] secretKey) {
11        this.publicKey = publicKey;
12        this.secretKey = secretKey;
13        if (publicKey.length != secretKey.length) {
14            throw new IllegalArgumentException("Different keys length");
15        }
16        countSecret = publicKey.length;
17    }
18
19    public int getSecret() {
20        int[] f = generateAdditionalArr();
21        int secret = 0;
22        int multiplyPublic = getMultiplyPublicWithout(-1);
23        for (int i = 0; i < countSecret; i++) {
24            secret = secret + (secretKey[i] * getMultiplyPublicWithout(i) * f[i]);
25        }
26        return secret % multiplyPublic;
27    }
28
29    private int[] generateAdditionalArr() {
30        int[] arr = new int[countSecret];
31        for (int i = 0; i < countSecret; i++) {
32            arr[i] = multiInverse(getMultiplyPublicWithout(i), publicKey[i]);
33        }
34        return arr;
35    }
36
37    private int getMultiplyPublicWithout(int withoutIndex) {
38        int res = 1;
39        for (int i = 0; i < countSecret; i++) {
40            if (i != withoutIndex) {
41                res *= publicKey[i];
42            }
43        }
44        return res;
45    }
46
47    private int multiInverse(long aa, long bb) {
48        long a = aa;
49        long b = bb;
50        long x = 0;
51        long y = 1;
52        long lastX = 1;
53        long lastY = 0;
54        long temp;
55        while (b != 0) {
56            long q = a / b;
57            long r = a % b;
58
59            a = b;
60            b = r;
61
62            temp = x;
63            x = lastX - q * x;
64            lastX = temp;
65
66            temp = y;
67            y = lastY - q * y;
68            lastY = temp;
69        }
70        return (int) ((lastX % bb + bb) % bb);
71    }
72}