I am trying to compare the SHA-256 hash values of the same file with Python and Java. However, in some instances, the Python hash value has leading zeros, whereas the Java version does not. For instance, hashing somefile.txt in both programs yields:
Python: 000c3720cf1066fcde30876f498f060b0b3ad4e21abd473588f1f31f10fdd890
Java : c3720cf1066fcde30876f498f060b0b3ad4e21abd473588f1f31f10fdd890
Is it safe to simply remove leading 0's and compare or is there an implementation which does not produce the leading zeros?
Python Code
def sha256sum(filename): h = hashlib.sha256() b = bytearray(128*1024) mv = memoryview(b) with open(filename, 'rb', buffering=0) as f: for n in iter(lambda : f.readinto(mv), 0): h.update(mv[:n]) return h.hexdigest() print(sha256sum('/somepath/somefile.txt')) # 000c3720cf1066fcde30876f498f060b0b3ad4e21abd473588f1f31f10fdd890 Java Code
public static String calculateSHA256(File updateFile) { MessageDigest digest; try { digest = MessageDigest.getInstance("SHA-256"); } catch (NoSuchAlgorithmException e) { Log.e(TAG, "Exception while getting digest", e); return null; } InputStream is; try { is = new FileInputStream(updateFile); } catch (FileNotFoundException e) { Log.e(TAG, "Exception while getting FileInputStream", e); return null; } byte[] buffer = new byte[8192]; int read; try { while ((read = is.read(buffer)) > 0) { digest.update(buffer, 0, read); } byte[] shaSum = digest.digest(); BigInteger bigInt = new BigInteger(1, shaSum); String output = bigInt.toString(16); return output; } catch (IOException e) { throw new RuntimeException("Unable to process file for SHA256", e); } finally { try { is.close(); } catch (IOException e) { Log.e(TAG, "Exception on closing SHA256 input stream", e); } } } Log.i("Output", calculateSHA256(somefile)) // I/Output: c3720cf1066fcde30876f498f060b0b3ad4e21abd473588f1f31f10fdd890 
BigInteger. I think that it is this that is stripping off leading zeros.