Bitcoin/address validation: Difference between revisions

=={{header|Dart}}==

This requires [https://pub.dev/packages/crypto Crypto package] to compile.

<lang dart>

import 'package:crypto/crypto.dart';

class Bitcoin {

final String ALPHABET =

"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";

List<int> bigIntToByteArray(BigInt data) {

String str;

bool neg = false;

if (data < BigInt.zero) {

str = (~data).toRadixString(16);

neg = true;

} else str = data.toRadixString(16);

int p = 0;

int len = str.length;

int blen = (len + 1) ~/ 2;

int boff = 0;

List bytes;

if (neg) {

if (len & 1 == 1) {

p = -1;

}

int byte0 = ~int.parse(str.substring(0, p + 2), radix: 16);

if (byte0 < -128) byte0 += 256;

if (byte0 >= 0) {

boff = 1;

bytes = new List<int>(blen + 1);

bytes[0] = -1;

bytes[1] = byte0;

} else {

bytes = new List<int>(blen);

bytes[0] = byte0;

}

for (int i = 1; i < blen; ++i) {

int byte = ~int.parse(str.substring(p + (i << 1), p + (i << 1) + 2),

radix: 16);

if (byte < -128) byte += 256;

bytes[i + boff] = byte;

}

} else {

if (len & 1 == 1) {

p = -1;

}

int byte0 = int.parse(str.substring(0, p + 2), radix: 16);

if (byte0 > 127) byte0 -= 256;

if (byte0 < 0) {

boff = 1;

bytes = new List<int>(blen + 1);

bytes[0] = 0;

bytes[1] = byte0;

} else {

bytes = new List<int>(blen);

bytes[0] = byte0;

}

for (int i = 1; i < blen; ++i) {

int byte =

int.parse(str.substring(p + (i << 1), p + (i << 1) + 2), radix: 16);

if (byte > 127) byte -= 256;

bytes[i + boff] = byte;

}

}

return bytes;

}

List<int> arrayCopy(bytes, srcOffset, result, destOffset, bytesLength) {

for (int i = srcOffset; i < bytesLength; i++) {

result[destOffset + i] = bytes[i];

}

return result;

}

List<int> decodeBase58To25Bytes(String input) {

BigInt number = BigInt.zero;

for (String t in input.split('')) {

int p = ALPHABET.indexOf(t);

if (p == (-1))

return null;

number = number * (BigInt.from(58)) + (BigInt.from(p));

}

List<int> result = new List<int>(24);

List<int> numBytes = bigIntToByteArray(number);

return arrayCopy(

numBytes, 0, result, result.length - numBytes.length, numBytes.length);

}

validateAddress(String address) {

List<int> decoded = new List.from(decodeBase58To25Bytes(address));

List<int> temp = new List<int>.from(decoded);

temp.insert(0, 0);

List<int> hash1 = sha256.convert(temp.sublist(0, 21)).bytes;

List<int> hash2 = sha256.convert(hash1).bytes;

if (hash2[0] != decoded[20] ||

hash2[1] != decoded[21] ||

hash2[2] != decoded[22] ||

hash2[3] != decoded[23]) return false;

return true;

}

}

</lang>

{{out}}

<pre>"1BNGaR29FmfAqidXmD9HLwsGv9p5WVvvhq" true

"1BNGaR29FmfAqidXmD9HLws" false

</pre>