Hash different data into SHA 256 - same results

Question

Existing SHA-256, how to update it with another or multiple different data types

    BigInteger d = new BigInteger("773182302672421767750165305491852205951657281488");
    BigInteger r = new BigInteger("1354751385705862203270732046669540660812388894970");
    String R_ID = "id_b";
    String C_ID = "id_b";

    MessageDigest sha_c = MessageDigest.getInstance("SHA-256");
    sha_c.update(r.toByteArray());
    sha_c.update(d.toByteArray());
    sha_c.update(C_ID.getBytes());
    System.out.println(Arrays.toString(sha_c.digest()));

    MessageDigest sha_b = MessageDigest.getInstance("SHA-256");
    sha_b.update(r.toByteArray());
    sha_b.update(d.toByteArray());
    sha_b.update(R_ID.getBytes());
    System.out.println(Arrays.toString(sha_b.digest()));

Same results: result with update with sha_c.update(C_ID.getBytes());

[114, -62, 50, -44, -118, 20, -29, 34, -112, 99, -17, -6, 97, -64, -121, 20, 30, -55, 110, 54, 9, -90, 100, 125, -28, 75, 106, -15, -87, -109, -51, 46]

result with update with sha_b.update(R_ID.getBytes());

[114, -62, 50, -44, -118, 20, -29, 34, -112, 99, -17, -6, 97, -64, -121, 20, 30, -55, 110, 54, 9, -90, 100, 125, -28, 75, 106, -15, -87, -109, -51, 46]

I do not see why it is a duplicate of this particular question. The question seems to be why the SHA-256 values are the same for different data. The answer is that SHA-256 depends solely on the data contents, and R_ID and C_ID are equal. BTW, the second example contains typos: d_c2 should be d_b2. — Jonathan Rosenne, Sep 22 '17 at 16:54
indeed, I don't see any problems in printing an array in this question. — eis, Sep 22 '17 at 17:00

score 0 · Accepted Answer · answered Sep 22 '17 at 23:13

You got the same results because you did the exact same thing twice.

BigInteger d = new BigInteger("773182302672421767750165305491852205951657281488");
BigInteger r = new BigInteger("1354751385705862203270732046669540660812388894970");
String R_ID = "id_b";
String C_ID = "id_b";

R_ID and C_ID contain the same value, so

MessageDigest sha_c = MessageDigest.getInstance("SHA-256");
sha_c.update(r.toByteArray());
sha_c.update(d.toByteArray());
sha_c.update(C_ID.getBytes());
System.out.println(Arrays.toString(sha_c.digest()));

MessageDigest sha_b = MessageDigest.getInstance("SHA-256");
sha_b.update(r.toByteArray());
sha_b.update(d.toByteArray());
sha_b.update(R_ID.getBytes());
System.out.println(Arrays.toString(sha_b.digest()));

is the exact same thing done twice. I assume this was not what you intended.

Hash different data into SHA 256 - same results

1 Answers1