DsaSignatureVerifier.java Test Results

Cryptography Tutorials - Herong's Tutorial Examples

∟DsaSignatureVerifier.java Test Results

This section provides test results from DsaSignatureVerifier.java on DSA digital signatures generated on a binary file. The verification will pass if the original document and the digital signature have not been modified.

Now let's see the verification result of the first DSA digital signature generated previously.

herong> java DsaSignatureVerifier \
   dsa_512.pub DsaSignatureGenerator.class dsa_512.sig

Public Key Info:
Algorithm = DSA

Signature Object Info:
Algorithm = SHA1withDSA
Provider = SUN version 12
Verify Processing Info:
Number of input bytes = 2859
Verification result = true

Cool. The signature verification passed. So nobody changed DsaSignatureGenerator.class or dsa_512.sig.

What will happen if DsaSignatureGenerator.class is changed? Let's create a modified version by adding characters to the end of the file:

herong> copy  DsaSignatureGenerator.class+con \
   DsaSignatureGenerator.modified

DsaSignatureGenerator.class
con
A^Z
        1 file(s) copied.

The DsaSignatureGenerator.java will tell us that the signature failed to pass the verification:

herong> java DsaSignatureVerifier dsa_512.pub \
   DsaSignatureGenerator.modified dsa_512.sig

Public Key Info:
Algorithm = DSA

Signature Object Info:
Algorithm = SHA1withDSA
Provider = SUN version 12
Verify Processing Info:
Number of input bytes = 529
Verification result = false

We can also verify the digital signature generated with the 1024-bit private key:

herong> java DsaSignatureVerifier \
   dsa_1024.pub DsaSignatureGenerator.class dsa_1024.sig

Public Key Info:
Algorithm = DSA

Signature Object Info:
Algorithm = SHA1withDSA
Provider = SUN version 12
Verify Processing Info:
Number of input bytes = 2859
Verification result = true