Data update

Task/Bitcoin-address-validation/Java/bitcoin-address-validation-2.java

@@ -0,0 +1,71 @@
+import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.List;
+
+public final class BitcoinAddressValidation {
+
+	public static void main(String[] args) {
+		List<String> addresses = List.of ( "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i",
+										   "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j",
+										   "1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9",
+										   "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X",
+										   "1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" );					
+		
+		for ( String address : addresses ) {
+			System.out.println(address + " : " + isValid(address));
+		}
+	}
+	
+	private static boolean isValid(String address) {
+		if ( address.length() < 26 || address.length() > 35 ) {
+			throw new AssertionError("Invalid length of bitcoin address");
+		}		
+		
+		byte[] decoded = decodeBase58(address);			
+		byte[] first21 = Arrays.copyOfRange(decoded, 0, 21);		
+		// Convert 'first21' into an ASCII string for the first SHA256 hash
+		String text = new String(first21, StandardCharsets.ISO_8859_1);	
+		String hashOne = SHA256.messageDigest(text);		
+		// Convert 'hashOne' into an ASCII string for the second SHA256 hash
+		byte[] bytesOne = hexToBytes(hashOne);	
+		String asciiOne = new String(bytesOne, StandardCharsets.ISO_8859_1);		
+		String hashTwo = SHA256.messageDigest(asciiOne);
+				
+		byte[] bytesTwo = hexToBytes(hashTwo);			
+		byte[] checksum = Arrays.copyOfRange(bytesTwo, 0, 4);		
+		byte[] last4 = Arrays.copyOfRange(decoded, 21, 25);	
+		return Arrays.equals(last4, checksum);		
+	}
+	
+	private static byte[] decodeBase58(String text) {
+        byte[] result = new byte[25];
+        for ( char ch : text.toCharArray() ) {
+            int index = ALPHABET.indexOf(ch);
+            if ( index == -1 ) {
+            	throw new AssertionError("Invalid character found in bitcoin address: " + ch);
+            }
+            for ( int i = result.length - 1; i > 0; i-- ) {
+                index += 58 * (int) ( result[i] & 0xFF );
+                result[i] = (byte) ( index & 0xFF );
+                index >>= 8;
+            }
+            if ( index != 0 ) {
+            	throw new AssertionError("Bitcoin address is too long");
+            }
+        }
+        return result;
+    }
+	
+	private static byte[] hexToBytes(String text) {
+		byte[] bytes = new byte[text.length() / 2];
+	    for ( int i = 0; i < text.length(); i += 2 ) {
+	    	 final int firstDigit = Character.digit(text.charAt(i), 16);
+	    	 final int secondDigit = Character.digit(text.charAt(i + 1), 16);
+	         bytes[i / 2] = (byte) ( ( firstDigit << 4 ) + secondDigit );
+	    }
+	    return bytes;
+	}
+
+	private static final String ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";  	
+
+}