Bitcoin/address validation

From Rosetta Code
Warning: Many of these snippets are incomplete. It is recommended that you use an established library for any projects that are likely to see external use
Task
Bitcoin/address validation
You are encouraged to solve this task according to the task description, using any language you may know.

Write a program that takes a bitcoin address as argument, and checks whether or not this address is valid.

A bitcoin address uses a base58 encoding, which uses an alphabet of the characters 0 .. 9, A ..Z, a .. z, but without the four characters 0, O, I and l.

With this encoding, a bitcoin address encodes 25 bytes:

  • the first byte is the version number, which will be zero for this task ;
  • the next twenty bytes are a RIPEMD-160 digest, but you don't have to know that for this task: you can consider them a pure arbitrary data ;
  • the last four bytes are a checksum check. They are the first four bytes of a double SHA-256 digest of the previous 21 bytes.

To check the bitcoin address, you must read the first twenty-one bytes, compute the checksum, and check that it corresponds to the last four bytes.

The program can either return a boolean value or throw an exception when not valid.

You can use a digest library for SHA-256.

Here is an example of a bitcoin address:

1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i

It does not belong to anyone. It is part of the test suite of the bitcoin software. You can change a few characters in this string and check that it will fail the test.


Ada[edit]

with Ada.Exceptions, Interfaces;
with Ada.Streams;
use Ada.Exceptions, Interfaces;
use Ada.Streams;
 
package Bitcoin is
subtype BT_Raw_Addr is Stream_Element_Array(1..25);
subtype BT_Checksum is Stream_Element_Array(1..4);
subtype BT_Addr is String(1..34);
subtype Sha256String is String(1..64);
Invalid_Address_Error : Exception;
 
function Double_Sha256(S : Stream_Element_Array) return BT_Checksum;
function Is_Valid(A : BT_Raw_Addr) return Boolean;
procedure Base58_Decode(S : BT_Addr; A : out BT_Raw_Addr) ;
private
Base58 : constant String := "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
function Hex_Val (C, C2 : Character) return Stream_Element;
end Bitcoin;
 
 
with GNAT.SHA256, Ada.Strings.Fixed;
use GNAT.SHA256, Ada.Strings.Fixed;
 
package body Bitcoin is
 
function Hex_Val (C, C2 : Character) return Stream_Element is
subtype Nibble is Integer range 0..15;
HEX : array (0..255) of Nibble := (
48=>0, 49=>1, 50=>2, 51=>3, 52=>4, 53=>5, 54=>6, 55=>7, 56=>8, 57=>9
, 65=>10, 66=>11, 67=>12, 68 =>13, 69 =>14, 70 =>15
, 97=>10, 98=>11, 99=>12, 100=>13, 101=>14, 102=>15
, Others=>0
);
begin
return Stream_Element(HEX(Character'Pos(C)) * 16 + HEX(Character'Pos(C2)));
end Hex_Val;
 
function Double_Sha256(S : Stream_Element_Array) return BT_Checksum is
Ctx  : Context := Initial_Context;
D : Message_Digest;
S2 : Stream_Element_Array(1..32);
Ctx2 : Context := Initial_Context;
C : BT_Checksum;
begin
Update(Ctx, S);
D := Digest(Ctx);
for I in S2'Range loop
S2(I) := Hex_Val(D(Integer(I)*2-1), D(Integer(I)*2));
end loop;
Update(Ctx2, S2);
D := Digest(Ctx2);
for I in C'Range loop
C(I) := Hex_Val(D(Integer(I)*2-1), D(Integer(I)*2));
end loop;
return C;
 
end Double_Sha256;
 
 
--------------------------------------------------------------------------------
-- Summary of Base58: --
-- We decode S into a 200 bit unsigned integer. --
-- We could use a BigNum library, but choose to go without. --
--------------------------------------------------------------------------------
procedure Base58_Decode(S : BT_Addr; A : out BT_Raw_Addr) is
begin
A := (Others => 0);
for I in S'Range loop
declare
P : Natural := Index(Base58, String(S(I..I)));
C : Natural;
begin
if P = 0 then
raise Invalid_Address_Error;
end if;
C := P - 1;
for J in reverse A'Range loop
C  := C + Natural(A(J)) * 58;
A(J) := Stream_Element(Unsigned_32(C) and 255); -- 0x00FF
C  := Natural(Shift_Right(Unsigned_32(C),8) and 255); -- 0xFF00
end loop;
if C /= 0 then
raise Invalid_Address_Error;
end if;
end;
end loop;
end Base58_Decode;
 
 
function Is_Valid(A : BT_Raw_Addr) return Boolean is
begin
return A(1) = 0 and A(22..25) = Double_Sha256(A(1..21));
end Is_Valid;
 
 
end Bitcoin;
 
with Ada.Text_IO, Bitcoin;
use Ada.Text_IO, Bitcoin;
 
procedure Bitcoin_Addr_Validate is
begin
declare
BTs : array (positive range <>) of BT_Addr := (
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" -- VALID
, "1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9" -- VALID
, "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X" -- checksum changed, original data.
, "1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" -- data changed, original checksum.
, "1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" -- invalid chars
);
begin
for I in Bts'Range loop
declare
A : BT_Raw_Addr;
Valid : Boolean;
begin
Put(BTs(I) & " validity: ");
Base58_Decode(BTs(I), A);
Valid := Is_Valid(A);
Put_Line(Boolean'Image(Valid));
exception
when E : Invalid_Address_Error =>
Put_Line ("*** Error: Invalid BT address.");
end;
end loop;
end;
end Bitcoin_Addr_Validate;
 
Output:
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i validity: TRUE
1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9 validity: TRUE
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X validity: FALSE
1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i validity: FALSE
1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i validity: *** Error: Invalid BT address.

C[edit]

#include <stdio.h>
#include <string.h>
#include <openssl/sha.h>
 
const char *coin_err;
#define bail(s) { coin_err = s; return 0; }
 
int unbase58(const char *s, unsigned char *out) {
static const char *tmpl = "123456789"
"ABCDEFGHJKLMNPQRSTUVWXYZ"
"abcdefghijkmnopqrstuvwxyz";
int i, j, c;
const char *p;
 
memset(out, 0, 25);
for (i = 0; s[i]; i++) {
if (!(p = strchr(tmpl, s[i])))
bail("bad char");
 
c = p - tmpl;
for (j = 25; j--; ) {
c += 58 * out[j];
out[j] = c % 256;
c /= 256;
}
 
if (c) bail("address too long");
}
 
return 1;
}
 
int valid(const char *s) {
unsigned char dec[32], d1[SHA256_DIGEST_LENGTH], d2[SHA256_DIGEST_LENGTH];
 
coin_err = "";
if (!unbase58(s, dec)) return 0;
 
SHA256(SHA256(dec, 21, d1), SHA256_DIGEST_LENGTH, d2);
 
if (memcmp(dec + 21, d2, 4))
bail("bad digest");
 
return 1;
}
 
int main (void) {
const char *s[] = {
"1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i",
"1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I",
0 };
int i;
for (i = 0; s[i]; i++) {
int status = valid(s[i]);
printf("%s: %s\n", s[i], status ? "Ok" : coin_err);
}
 
return 0;
}

Compile with -lcrypto

Output:
1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9: Ok
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i: Ok
1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9: bad digest
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I: bad char

C#[edit]

This requires NUnit package to compile.

 
using System;
using System.Linq;
using System.Security.Cryptography;
using NUnit.Framework;
 
namespace BitcoinValidator
{
public class ValidateTest
{
[TestCase]
public void ValidateBitcoinAddressTest()
{
Assert.IsTrue(ValidateBitcoinAddress("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i")); // VALID
Assert.IsTrue(ValidateBitcoinAddress("1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9")); // VALID
Assert.Throws<Exception>(() => ValidateBitcoinAddress("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X")); // checksum changed, original data
Assert.Throws<Exception>(() => ValidateBitcoinAddress("1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i")); // data changed, original checksum
Assert.Throws<Exception>(() => ValidateBitcoinAddress("1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i")); // invalid chars
Assert.Throws<Exception>(() => ValidateBitcoinAddress("BZbvjr")); // checksum is fine, address too short
}
 
public static bool ValidateBitcoinAddress(string address)
{
if (address.Length < 26 || address.Length > 35) throw new Exception("wrong length");
var decoded = DecodeBase58(address);
var d1 = Hash(decoded.SubArray(0, 21));
var d2 = Hash(d1);
if (!decoded.SubArray(21, 4).SequenceEqual(d2.SubArray(0, 4))) throw new Exception("bad digest");
return true;
}
 
const string Alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
const int Size = 25;
 
private static byte[] DecodeBase58(string input)
{
var output = new byte[Size];
foreach (var t in input)
{
var p = Alphabet.IndexOf(t);
if (p == -1) throw new Exception("invalid character found");
var j = Size;
while (--j > 0)
{
p += 58 * output[j];
output[j] = (byte)(p % 256);
p /= 256;
}
if (p != 0) throw new Exception("address too long");
}
return output;
}
 
private static byte[] Hash(byte[] bytes)
{
var hasher = new SHA256Managed();
return hasher.ComputeHash(bytes);
}
}
 
public static class ArrayExtensions
{
public static T[] SubArray<T>(this T[] data, int index, int length)
{
var result = new T[length];
Array.Copy(data, index, result, 0, length);
return result;
}
}
}
 

D[edit]

This requires the D module from the SHA-256 Task.

Translation of: Go
import std.stdio, std.algorithm, std.array, std.string, sha_256_2;
 
struct A25 {
// Type for a 25 ubyte (not base58 encoded) bitcoin address.
ubyte[25] enc;
 
ubyte bitcoinVersion() const pure nothrow @safe @nogc {
return enc[0];
}
 
ubyte[4] embeddedChecksum() return const pure nothrow @safe @nogc {
return enc[$ - 4 .. $];
}
 
/** Computes a double sha256 hash of the first 21 bytes of
the address. Returns the full 32 ubyte sha256 hash. */

ubyte[32] doubleSHA256() const pure nothrow @nogc {
return SHA256.digest(SHA256.digest(enc[0 .. 21]));
}
 
/** Returns a four ubyte checksum computed from the first 21
bytes of the address. */

ubyte[4] computeChecksum() const pure nothrow @nogc {
return doubleSHA256[0 .. 4];
}
 
/** Takes a base58 encoded address and decodes it into the
receiver. Errors are returned if the argument is not valid base58
or if the decoded value does not fit in the 25 ubyte address.
The address is not otherwise checked for validity. */

string set58(in ubyte[] s) pure nothrow @safe @nogc {
static immutable digits =
"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
.representation;
static assert(digits.length == 58);
 
foreach (immutable char s1; s) {
immutable c = digits.countUntil(s1);
if (c < 0)
return "found a bad char in the Bitcoin address.";
 
// Currently the D type system can't see c as nonegative.
uint uc = (c < 0) ? 0 : c;
 
foreach_reverse (ref aj; enc) {
uc += digits.length * aj;
aj = uc % 256;
uc /= 256;
}
if (uc > 0)
return "too long Bitcoin address.";
}
 
return null;
}
}
 
/** Validates a base58 encoded bitcoin address. An address is valid
if it can be decoded into a 25 ubyte address, the Version number is 0,
and the checksum validates. Return value ok will be true for valid
addresses. If ok is false, the address is invalid and the error value
may indicate why. */

string isValidA58(in ubyte[] a58) pure nothrow @nogc {
A25 a;
immutable err = a.set58(a58);
if (!err.empty)
return err;
if (a.bitcoinVersion != 0)
return "not Bitcoin version 0.";
return (a.embeddedChecksum == a.computeChecksum) ? null :
"checksums don't match.";
}
 
void main() {
immutable tests = ["1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62!",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62iz",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz"];
 
foreach (immutable test; tests) {
immutable err = test.representation.isValidA58;
writefln(`"%s": %s`, test, err.empty ? "OK." : err);
}
}
Output:
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i": OK.
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j": checksums don't match.
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62!": found a bad char in the Bitcoin address.
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62iz": not Bitcoin version 0.
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz": too long Bitcoin address.

Erlang[edit]

Using base58 module from http://github.com/titan098/erl-base58.git.

 
-module( bitcoin_address ).
 
-export( [task/0, validate/1] ).
 
task() ->
io:fwrite( "Validate ~p~n", ["1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i"] ),
io:fwrite( "~p~n", [validate("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i")] ),
io:fwrite( "Validate ~p~n", ["1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW622"] ),
io:fwrite( "~p~n", [validate("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW622")] ).
 
validate( String ) ->
{length_25, <<Address:21/binary, Checksum:4/binary>>} = {length_25, base58:base58_to_binary( String )},
<<Version:1/binary, _/binary>> = Address,
{version_0, <<0>>} = {version_0, Version},
<<Four_bytes:4/binary, _T/binary>> = crypto:hash( sha256, crypto:hash(sha256, Address) ),
{checksum, Checksum} = {checksum, Four_bytes},
ok.
 
Output:
17>  bitcoin_address:task().
Validate "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i"
ok
Validate "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW622"
** exception error: no match of right hand side value {checksum,<<"ÀF²ÿ">>}
     in function  bitcoin_address:validate/1 (src/bitcoin_address.erl, line 16)
     in call from bitcoin_address:task/0 (src/bitcoin_address.erl, line 9)

Factor[edit]

USING: byte-arrays checksums checksums.sha io.binary kernel math
math.parser sequences ;
IN: rosetta-code.bitcoin.validation
 
CONSTANT: ALPHABET "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
 
: base58>bigint ( str -- n )
[ ALPHABET index ]
[ [ 58 * ] [ + ] bi* ] map-reduce ;
 
: base58> ( str -- bytes ) base58>bigint 25 >be ;
 
: btc-checksum ( bytes -- checksum-bytes )
21 head 2 [ sha-256 checksum-bytes ] times 4 head ;
 
: btc-valid? ( str -- ? ) base58> [ btc-checksum ] [ 4 tail* ] bi = ;
 
Output:
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" btc-valid? . ! t, VALID
"1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9" btc-valid? . ! t, VALID
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X" btc-valid? . ! f, checksum changed, original data.
"1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" btc-valid? . ! f, data changed, original checksum.

FreeBASIC[edit]

' version 05-04-2017
' compile with: fbc -s console
 
' function adapted from the SHA-256 task
Function SHA_256(test_str As String, bitcoin As ULong = 0) As String
 
#Macro Ch (x, y, z)
(((x) And (y)) Xor ((Not (x)) And z))
#EndMacro
 
#Macro Maj (x, y, z)
(((x) And (y)) Xor ((x) And (z)) Xor ((y) And (z)))
#EndMacro
 
#Macro sigma0 (x)
(((x) Shr 2 Or (x) Shl 30) Xor ((x) Shr 13 Or (x) Shl 19) Xor ((x) Shr 22 Or (x) Shl 10))
#EndMacro
 
#Macro sigma1 (x)
(((x) Shr 6 Or (x) Shl 26) Xor ((x) Shr 11 Or (x) Shl 21) Xor ((x) Shr 25 Or (x) Shl 7))
#EndMacro
 
#Macro sigma2 (x)
(((x) Shr 7 Or (x) Shl 25) Xor ((x) Shr 18 Or (x) Shl 14) Xor ((x) Shr 3))
#EndMacro
 
#Macro sigma3 (x)
(((x) Shr 17 Or (x) Shl 15) Xor ((x) Shr 19 Or (x) Shl 13) Xor ((x) Shr 10))
#EndMacro
 
Dim As String message = test_str ' strings are passed as ByRef's
 
Dim As Long i, j
Dim As UByte Ptr ww1
Dim As UInteger<32> Ptr ww4
 
Do
Dim As ULongInt l = Len(message)
' set the first bit after the message to 1
message = message + Chr(1 Shl 7)
' add one char to the length
Dim As ULong padding = 64 - ((l +1) Mod (512 \ 8)) ' 512 \ 8 = 64 char.
 
' check if we have enough room for inserting the length
If padding < 8 Then padding = padding + 64
 
message = message + String(padding, Chr(0)) ' adjust length
Dim As ULong l1 = Len(message) ' new length
 
l = l * 8 ' orignal length in bits
' create ubyte ptr to point to l ( = length in bits)
Dim As UByte Ptr ub_ptr = Cast(UByte Ptr, @l)
 
For i = 0 To 7 'copy length of message to the last 8 bytes
message[l1 -1 - i] = ub_ptr[i]
Next
 
'table of constants
Dim As UInteger<32> K(0 To ...) = _
{ &H428a2f98, &H71374491, &Hb5c0fbcf, &He9b5dba5, &H3956c25b, &H59f111f1, _
&H923f82a4, &Hab1c5ed5, &Hd807aa98, &H12835b01, &H243185be, &H550c7dc3, _
&H72be5d74, &H80deb1fe, &H9bdc06a7, &Hc19bf174, &He49b69c1, &Hefbe4786, _
&H0fc19dc6, &H240ca1cc, &H2de92c6f, &H4a7484aa, &H5cb0a9dc, &H76f988da, _
&H983e5152, &Ha831c66d, &Hb00327c8, &Hbf597fc7, &Hc6e00bf3, &Hd5a79147, _
&H06ca6351, &H14292967, &H27b70a85, &H2e1b2138, &H4d2c6dfc, &H53380d13, _
&H650a7354, &H766a0abb, &H81c2c92e, &H92722c85, &Ha2bfe8a1, &Ha81a664b, _
&Hc24b8b70, &Hc76c51a3, &Hd192e819, &Hd6990624, &Hf40e3585, &H106aa070, _
&H19a4c116, &H1e376c08, &H2748774c, &H34b0bcb5, &H391c0cb3, &H4ed8aa4a, _
&H5b9cca4f, &H682e6ff3, &H748f82ee, &H78a5636f, &H84c87814, &H8cc70208, _
&H90befffa, &Ha4506ceb, &Hbef9a3f7, &Hc67178f2 }
 
Dim As UInteger<32> h0 = &H6a09e667
Dim As UInteger<32> h1 = &Hbb67ae85
Dim As UInteger<32> h2 = &H3c6ef372
Dim As UInteger<32> h3 = &Ha54ff53a
Dim As UInteger<32> h4 = &H510e527f
Dim As UInteger<32> h5 = &H9b05688c
Dim As UInteger<32> h6 = &H1f83d9ab
Dim As UInteger<32> h7 = &H5be0cd19
Dim As UInteger<32> a, b, c, d, e, f, g, h
Dim As UInteger<32> t1, t2, w(0 To 63)
 
For j = 0 To (l1 -1) \ 64 ' split into block of 64 bytes
ww1 = Cast(UByte Ptr, @message[j * 64])
ww4 = Cast(UInteger<32> Ptr, @message[j * 64])
 
For i = 0 To 60 Step 4 'little endian -> big endian
Swap ww1[i ], ww1[i +3]
Swap ww1[i +1], ww1[i +2]
Next
 
For i = 0 To 15 ' copy the 16 32bit block into the array
W(i) = ww4[i]
Next
 
For i = 16 To 63 ' fill the rest of the array
w(i) = sigma3(W(i -2)) + W(i -7) + sigma2(W(i -15)) + W(i -16)
Next
 
a = h0 : b = h1 : c = h2 : d = h3 : e = h4 : f = h5 : g = h6 : h = h7
 
For i = 0 To 63
t1 = h + sigma1(e) + Ch(e, f, g) + K(i) + W(i)
t2 = sigma0(a) + Maj(a, b, c)
h = g : g = f : f = e
e = d + t1
d = c : c = b : b = a
a = t1 + t2
Next
 
h0 += a : h1 += b : h2 += c : h3 += d
h4 += e : h5 += f : h6 += g : h7 += h
 
Next j
 
Dim As String answer = Hex(h0, 8) + Hex(h1, 8) + Hex(h2, 8) + Hex(h3, 8) _
+ Hex(h4, 8) + Hex(h5, 8) + Hex(h6, 8) + Hex(h7, 8)
 
If bitcoin = 0 Then
Return LCase(answer)
Else 'conver hex value's to integer value's
message = String(32,0)
For i = 0 To 31
message[i] = Val("&h" + Mid(answer, i * 2 + 1, 2))
Next
bitcoin = 0
End If
 
Loop
 
End Function
 
Function conv_base58(bitcoin_address As String) As String
 
Dim As String base58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
Dim As String tmp = String(24, 0)
Dim As Long x, y, z
 
For x = 1 To Len(bitcoin_address) -1
z = InStr(base58, Chr(bitcoin_address[x])) -1
If z = -1 Then
Print " bitcoin address contains illegal character"
Return ""
End If
For y = 23 To 0 Step -1
z = z + tmp[y] * 58
tmp[y] = z And 255 ' test_str[y] = z Mod 256
z Shr= 8 ' z \= 256
Next
If z <> 0 Then
Print " bitcoin address is to long"
Return ""
End If
Next
 
z = InStr(base58, Chr(bitcoin_address[0])) -1
Return Chr(z) + tmp
 
End Function
 
' ------=< MAIN >=------
 
Data "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" ' original
Data "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j" ' checksum changed
Data "1NAGa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" ' address changed
Data "0AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" ' only 1 or 3 as first char. allowed
Data "1AGNa15ZQXAZUgFlqJ2i7Z2DPU2J6hW62i" ' illegal character in address
 
Dim As String tmp, result, checksum, bitcoin_address
Dim As Long i, j
 
For i = 1 To 5
 
Read bitcoin_address
Print "Bitcoin address: "; bitcoin_address;
tmp = Left(bitcoin_address,1)
 
If tmp <> "1" And tmp <> "3" Then
Print " first character is not 1 or 3"
Continue For
End If
 
' convert bitcoinaddress
tmp = conv_base58(bitcoin_address)
If tmp = "" Then Continue For
' get the checksum, last 4 digits
For j As Long = 21 To 24
checksum = checksum + LCase(Hex(tmp[j], 2))
Next
 
' send the first 21 characters to the SHA 256 routine
result = SHA_256(Left(tmp, 21), 2)
result = Left(result, 8) ' get the checksum (the first 8 digits (hex))
If checksum = result Then ' test the found checksum against
Print " is valid" ' the one from the address
Else
Print " is not valid, checksum fails"
End If
 
Next
 
' empty keyboard buffer
While InKey <> "" : Wend
Print : Print "hit any key to end program"
Sleep
End
Output:
Bitcoin address: 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i is valid
Bitcoin address: 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j is not valid, checksum fails
Bitcoin address: 1NAGa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i is not valid, checksum fails
Bitcoin address: 0AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i first character is not 1 or 3
Bitcoin address: 1AGNa15ZQXAZUgFlqJ2i7Z2DPU2J6hW62i bitcoin address contains illegal character

Go[edit]

Translation of: C
package main
 
import (
"bytes"
"crypto/sha256"
"errors"
"os"
)
 
// With at least one other bitcoin RC task, this source is styled more like
// a package to show how functions of the two tasks might be combined into
// a single package. It turns out there's not really that much shared code,
// just the A25 type and doubleSHA256 method, but it's enough to suggest how
// the code might be organized. Types, methods, and functions are capitalized
// where they might be exported from a package.
 
// A25 is a type for a 25 byte (not base58 encoded) bitcoin address.
type A25 [25]byte
 
func (a *A25) Version() byte {
return a[0]
}
 
func (a *A25) EmbeddedChecksum() (c [4]byte) {
copy(c[:], a[21:])
return
}
 
// DoubleSHA256 computes a double sha256 hash of the first 21 bytes of the
// address. This is the one function shared with the other bitcoin RC task.
// Returned is the full 32 byte sha256 hash. (The bitcoin checksum will be
// the first four bytes of the slice.)
func (a *A25) doubleSHA256() []byte {
h := sha256.New()
h.Write(a[:21])
d := h.Sum([]byte{})
h = sha256.New()
h.Write(d)
return h.Sum(d[:0])
}
 
// ComputeChecksum returns a four byte checksum computed from the first 21
// bytes of the address. The embedded checksum is not updated.
func (a *A25) ComputeChecksum() (c [4]byte) {
copy(c[:], a.doubleSHA256())
return
}/* {{header|Go}} */
 
// Tmpl and Set58 are adapted from the C solution.
// Go has big integers but this techinique seems better.
var tmpl = []byte("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz")
 
// Set58 takes a base58 encoded address and decodes it into the receiver.
// Errors are returned if the argument is not valid base58 or if the decoded
// value does not fit in the 25 byte address. The address is not otherwise
// checked for validity.
func (a *A25) Set58(s []byte) error {
for _, s1 := range s {
c := bytes.IndexByte(tmpl, s1)
if c < 0 {
return errors.New("bad char")
}
for j := 24; j >= 0; j-- {
c += 58 * int(a[j])
a[j] = byte(c % 256)
c /= 256
}
if c > 0 {
return errors.New("too long")
}
}
return nil
}
 
// ValidA58 validates a base58 encoded bitcoin address. An address is valid
// if it can be decoded into a 25 byte address, the version number is 0,
// and the checksum validates. Return value ok will be true for valid
// addresses. If ok is false, the address is invalid and the error value
// may indicate why.
func ValidA58(a58 []byte) (ok bool, err error) {
var a A25
if err := a.Set58(a58); err != nil {
return false, err
}
if a.Version() != 0 {
return false, errors.New("not version 0")
}
return a.EmbeddedChecksum() == a.ComputeChecksum(), nil
}
 
// Program returns exit code 0 with valid address and produces no output.
// Otherwise exit code is 1 and a message is written to stderr.
func main() {
if len(os.Args) != 2 {
errorExit("Usage: valid <base58 address>")
}
switch ok, err := ValidA58([]byte(os.Args[1])); {
case ok:
case err == nil:
errorExit("Invalid")
default:
errorExit(err.Error())
}
}
 
func errorExit(m string) {
os.Stderr.WriteString(m + "\n")
os.Exit(1)
}
Output:

Command line usage examples showing program exit status.

> valid ; echo $status
Usage: valid <base58 address>
1
> valid 1 1 ; echo $status
Usage: valid <base58 address>
1
> valid 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i ; echo $status
0
> valid 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j ; echo $status
Invalid
1
> valid 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62! ; echo $status
bad char
1
> valid 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62iz ; echo $status
not version 0
1
> valid 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz ; echo $status
too long
1

Haskell[edit]

import Data.List (unfoldr, elemIndex)
import Data.Binary (Word8)
import Crypto.Hash.SHA256 (hash)
import Data.ByteString (unpack, pack)
 
-- Convert from base58 encoded value to Integer
decode58 :: String -> Maybe Integer
decode58 = foldl (\v d -> (+) <$> ((58*) <$> v) <*> (fromIntegral <$> elemIndex d c58 )) $ Just 0
where c58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
 
-- Convert from base58 encoded value to list of bytes
toBytes :: Integer -> [Word8]
toBytes x = reverse $ unfoldr (\b -> if b == 0 then Nothing else Just (fromIntegral $ b `mod` 256, b `div` 256)) x
 
-- Check validity of base58 encoded bitcoin address.
-- Result is either an error string (Left) or a validity bool (Right).
validityCheck :: String -> Either String Bool
validityCheck encodedAddress =
let d58 = decode58 encodedAddress
in case d58 of
Nothing -> Left "Invalid base 58 encoding"
Just ev ->
let address = toBytes ev
addressLength = length address
in if addressLength > 25
then Left "Address length exceeds 25 bytes"
else
if addressLength < 4
then Left "Address length less than 4 bytes"
else
let (bs,cs) = splitAt 21 $ replicate (25 - addressLength) 0 ++ address
in Right $ all (uncurry (==)) (zip cs $ unpack $ hash $ hash $ pack bs)
 
-- Run one validity check and display results.
validate :: String -> IO ()
validate encodedAddress =
let vc = validityCheck encodedAddress
in case vc of
Left err ->
putStrLn $ show encodedAddress ++ " -> " ++ show err
Right validity ->
putStrLn $ show encodedAddress ++ " -> " ++ if validity then "Valid" else "Invalid"
 
-- Run some validity check tests.
main :: IO ()
main = do
validate "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" -- VALID
validate "1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9" -- VALID
validate "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X" -- checksum changed, original data.
validate "1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" -- data changed, original checksum.
validate "1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" -- invalid chars
validate "1ANa55215ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" -- too long
validate "i55j" -- too short
Output:
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" -> Valid
"1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9" -> Valid
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X" -> Invalid
"1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" -> Invalid
"1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" -> "Invalid base 58 encoding"
"1ANa55215ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" -> "Address length exceeds 25 bytes"
"i55j" -> "Address length less than 4 bytes"

Mathematica / Wolfram Language[edit]

chars = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"; data = 
IntegerDigits[
FromDigits[
StringPosition[chars, #][[1]] - 1 & /@ Characters[InputString[]],
58], 256, 25];
data[[-4 ;;]] ==
IntegerDigits[
Hash[FromCharacterCode[
IntegerDigits[Hash[FromCharacterCode[data[[;; -5]]], "SHA256"],
256, 32]], "SHA256"], 256, 32][[;; 4]]
Input:
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i
2AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i
Output:
True
False


Java[edit]

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
 
public class BitcoinAddressValidator {
 
private static final String ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
 
public static boolean validateBitcoinAddress(String addr) {
if (addr.length() < 26 || addr.length() > 35)
return false;
byte[] decoded = decodeBase58(addr, 25);
if (decoded == null)
return false;
 
byte[] hash1 = sha256(Arrays.copyOfRange(decoded, 0, 21));
byte[] hash2 = sha256(hash1);
 
return Arrays.equals(Arrays.copyOfRange(hash2, 0, 4), Arrays.copyOfRange(decoded, 21, 25));
}
 
private static byte[] decodeBase58(String input, int len) {
byte[] output = new byte[len];
for (char t : input.toCharArray()) {
int p = ALPHABET.indexOf(t);
if (p == -1)
return null;
for (int j = len - 1; j >= 0; j--) {
p += 58 * (output[j] & 0xFF);
output[j] = (byte) (p % 256);
p /= 256;
}
if (p != 0)
return null;
}
 
return output;
}
 
private static byte[] sha256(byte[] data) {
try {
MessageDigest md = MessageDigest.getInstance("SHA-256");
md.update(data);
return md.digest();
} catch (NoSuchAlgorithmException e) {
throw new IllegalStateException(e);
}
}
 
public static void main(String[] args) {
assertBitcoin("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i", true);
assertBitcoin("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j", false);
assertBitcoin("1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9", true);
assertBitcoin("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X", false);
assertBitcoin("1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i", false);
assertBitcoin("1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i", false);
assertBitcoin("BZbvjr", false);
assertBitcoin("i55j", false);
assertBitcoin("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62!", false);
assertBitcoin("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62iz", false);
assertBitcoin("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz", false);
assertBitcoin("1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9", false);
assertBitcoin("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I", false);
}
 
private static void assertBitcoin(String address, boolean expected) {
boolean actual = validateBitcoinAddress(address);
if (actual != expected)
throw new AssertionError(String.format("Expected %s for %s, but got %s.", expected, address, actual));
}
}

Julia[edit]

Works with: Julia version 0.6
Translation of: Python
using SHA
 
bytes(n::Integer, l::Int) = collect(UInt8, (n >> 8i) & 0xFF for i in l-1:-1:0)
 
function decodebase58(bc::String, l::Int)
digits = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
num = big(0)
for c in bc
num = num * 58 + search(digits, c) - 1
end
return bytes(num, l)
end
 
function checkbcaddress(addr::String)
if !(25 ≤ length(addr) ≤ 35) return false end
bcbytes = decodebase58(addr, 25)
sha = sha256(sha256(bcbytes[1:end-4]))
return bcbytes[end-3:end] == sha[1:4]
end
 
const addresses = Dict(
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" => true,
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j" => false,
"1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9" => true,
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X" => true,
"1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" => false,
"1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" => false,
"BZbvjr" => false,
"i55j" => false,
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62!" => false,
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62iz" => false,
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz" => false,
"1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9" => false,
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I" => false)
 
for (addr, corr) in addresses
println("Address: $addr\nExpected: $corr\tChecked: ", checkbcaddress(addr))
end
Output:
Address: 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X
Expected: true	Checked: false
Address: 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i
Expected: true	Checked: true
Address: 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j
Expected: false	Checked: false
Address: 1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i
Expected: false	Checked: false
Address: 1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9
Expected: true	Checked: true
Address: BZbvjr
Expected: false	Checked: false
Address: 1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i
Expected: false	Checked: false
Address: i55j
Expected: false	Checked: false
Address: 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz
Expected: false	Checked: false
Address: 1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9
Expected: false	Checked: false
Address: 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62!
Expected: false	Checked: false
Address: 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I
Expected: false	Checked: false
Address: 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62iz
Expected: false	Checked: false

Kotlin[edit]

Translation of: Java
import java.security.MessageDigest
 
object Bitcoin {
private const val ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
 
private fun ByteArray.contentEquals(other: ByteArray): Boolean {
if (this.size != other.size) return false
return (0 until this.size).none { this[it] != other[it] }
}
 
private fun decodeBase58(input: String): ByteArray? {
val output = ByteArray(25)
for (c in input) {
var p = ALPHABET.indexOf(c)
if (p == -1) return null
for (j in 24 downTo 1) {
p += 58 * (output[j].toInt() and 0xff)
output[j] = (p % 256).toByte()
p = p shr 8
}
if (p != 0) return null
}
return output
}
 
private fun sha256(data: ByteArray, start: Int, len: Int, recursion: Int): ByteArray {
if (recursion == 0) return data
val md = MessageDigest.getInstance("SHA-256")
md.update(data.sliceArray(start until start + len))
return sha256(md.digest(), 0, 32, recursion - 1)
}
 
fun validateAddress(address: String): Boolean {
if (address.length !in 26..35) return false
val decoded = decodeBase58(address)
if (decoded == null) return false
val hash = sha256(decoded, 0, 21, 2)
return hash.sliceArray(0..3).contentEquals(decoded.sliceArray(21..24))
}
}
 
fun main(args: Array<String>) {
val addresses = arrayOf(
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j",
"1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X",
"1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i",
"1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i",
"BZbvjr",
"i55j",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62!",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62iz",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz",
"1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I"
)
for (address in addresses)
println("${address.padEnd(36)} -> ${if (Bitcoin.validateAddress(address)) "valid" else "invalid"}")
}
Output:
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i   -> valid
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j   -> invalid
1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9   -> valid
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X   -> invalid
1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i   -> invalid
1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i   -> invalid
BZbvjr                               -> invalid
i55j                                 -> invalid
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62!   -> invalid
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62iz  -> invalid
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz -> invalid
1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9   -> invalid
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I   -> invalid

Oberon-2[edit]

Works with: oo2c
Library: Crypto
 
MODULE BitcoinAddress;
IMPORT
Object,
NPCT:Tools,
Crypto:SHA256,
S := SYSTEM,
Out;
 
CONST
BASE58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
TYPE
BC_RAW = ARRAY 25 OF CHAR;
SHA256_HASH = ARRAY 32 OF CHAR;
 
VAR
b58: Object.CharsLatin1;
 
PROCEDURE IndexOfB58Char(c: CHAR): INTEGER;
VAR
i: INTEGER;
BEGIN
i := 0;
WHILE (b58[i] # 0X) & (b58[i] # c) DO INC(i) END;
IF b58[i] = 0X THEN RETURN -1 ELSE RETURN i END
END IndexOfB58Char;
 
PROCEDURE DecodeB58(s [NO_COPY]: ARRAY OF CHAR;VAR out: BC_RAW): BOOLEAN;
VAR
i,j,k: LONGINT;
 
BEGIN
FOR i := 0 TO LEN(out) - 1 DO; out[i] := CHR(0) END;
i := 0;
WHILE (s[i] # 0X) DO;
k := IndexOfB58Char(s[i]);
IF k < 0 THEN
Out.String("Error: Bad base58 character");Out.Ln;
RETURN FALSE
END;
FOR j := LEN(out) - 1 TO 0 BY -1 DO
k := k + 58 * ORD(out[j]);
out[j] := CHR(k MOD 256);
k := k DIV 256;
END;
 
IF k # 0 THEN Out.String("Error: Address to long");Out.Ln; RETURN FALSE END;
INC(i)
END;
RETURN TRUE
END DecodeB58;
 
PROCEDURE Valid(s [NO_COPY]: ARRAY OF CHAR): BOOLEAN;
VAR
dec: BC_RAW;
d1, d2: SHA256.Hash;
d1Str, d2Str: SHA256_HASH;
x,y: LONGINT;
BEGIN
Out.String(s);Out.String(" is valid? ");
IF ~DecodeB58(s,dec) THEN RETURN FALSE END;
 
d1 := SHA256.NewHash();d1.Initialize();
d2 := SHA256.NewHash();d2.Initialize();
d1.Update(dec,0,21);d1.GetHash(d1Str,0);
d2.Update(d1Str,0,d1.size);d2.GetHash(d2Str,0);
 
S.MOVE(S.ADR(dec) + 21,S.ADR(x),4);
S.MOVE(S.ADR(d2Str),S.ADR(y),4);
 
RETURN (x = y)
END Valid;
 
BEGIN
b58 := Tools.AsString(BASE58);
 
Out.Bool(Valid("1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9"));Out.Ln;
Out.Bool(Valid("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i"));Out.Ln;
Out.Bool(Valid("1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9"));Out.Ln;
Out.Bool(Valid("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I"));Out.Ln
END BitcoinAddress.
 
Output:
1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9 is valid? TRUE
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i is valid? TRUE
1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9 is valid? FALSE
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I is valid? Error: Bad base58 character
FALSE

Perl[edit]

my @b58 = qw{
1 2 3 4 5 6 7 8 9
A B C D E F G H J K L M N P Q R S T U V W X Y Z
a b c d e f g h i j k m n o p q r s t u v w x y z
};
my %b58 = map { $b58[$_] => $_ } 0 .. 57;
 
sub unbase58 {
use integer;
my @out;
my $azeroes = length($1) if $_[0] =~ /^(1*)/;
for my $c ( map { $b58{$_} } $_[0] =~ /./g ) {
for (my $j = 25; $j--; ) {
$c += 58 * ($out[$j] // 0);
$out[$j] = $c % 256;
$c /= 256;
}
}
my $bzeroes = length($1) if join('', @out) =~ /^(0*)/;
die "not a 25 byte address\n" if $bzeroes != $azeroes;
return @out;
}
 
sub check_bitcoin_address {
# Does nothing if address is valid
# dies otherwise
use Digest::SHA qw(sha256);
my @byte = unbase58 shift;
die "wrong checksum\n" unless
(pack 'C*', @byte[21..24]) eq
substr sha256(sha256 pack 'C*', @byte[0..20]), 0, 4;
}

Perl 6[edit]

my $bitcoin-address = rx/
<+alnum-[0IOl]> ** 26..* # an address is at least 26 characters long
<?{
use Digest::SHA;
.subbuf(21, 4) eqv sha256(sha256 .subbuf(0, 21)).subbuf(0, 4) given
Blob.new: <
1 2 3 4 5 6 7 8 9
A B C D E F G H J K L M N P Q R S T U V W X Y Z
a b c d e f g h i j k m n o p q r s t u v w x y z
>.pairs.invert.hash{$/.comb}
.reduce(* * 58 + *)
.polymod(256 xx 24)
.reverse;
}>
/;
 
say "Here is a bitcoin address: 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i" ~~ $bitcoin-address;
Output:
「1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i」

PHP[edit]

 
function validate($address){
$decoded = decodeBase58($address);
 
$d1 = hash("sha256", substr($decoded,0,21), true);
$d2 = hash("sha256", $d1, true);
 
if(substr_compare($decoded, $d2, 21, 4)){
throw new \Exception("bad digest");
}
return true;
}
function decodeBase58($input) {
$alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
 
$out = array_fill(0, 25, 0);
for($i=0;$i<strlen($input);$i++){
if(($p=strpos($alphabet, $input[$i]))===false){
throw new \Exception("invalid character found");
}
$c = $p;
for ($j = 25; $j--; ) {
$c += (int)(58 * $out[$j]);
$out[$j] = (int)($c % 256);
$c /= 256;
$c = (int)$c;
}
if($c != 0){
throw new \Exception("address too long");
}
}
 
$result = "";
foreach($out as $val){
$result .= chr($val);
}
 
return $result;
}
 
function main () {
$s = array(
"1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i",
"1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I",
);
foreach($s as $btc){
$message = "OK";
try{
validate($btc);
}catch(\Exception $e){ $message = $e->getMessage(); }
echo "$btc: $message\n";
}
}
 
main();
 
 
Output:
1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9: OK
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i: OK
1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9: bad digest
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I: invalid character found

PicoLisp[edit]

(load "sha256.l")
 
(setq *Alphabet
(chop "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz") )
(de unbase58 (Str)
(let (Str (chop Str) Lst (need 25 0) C)
(while (setq C (dec (index (pop 'Str) *Alphabet)))
(for (L Lst L)
(set
L (& (inc 'C (* 58 (car L))) 255)
'C (/ C 256) )
(pop 'L) ) )
(flip Lst) ) )
(de valid (Str)
(and
(setq @@ (unbase58 Str))
(=
(head 4 (sha256 (sha256 (head 21 @@))))
(tail 4 @@) ) ) )
(test
T
(valid "17NdbrSGoUotzeGCcMMCqnFkEvLymoou9j") )
(test
T
(=
NIL
(valid "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j")
(valid "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62!")
(valid "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62iz")
(valid "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz") ) )

PureBasic[edit]

 
; using PureBasic 5.50 (x64)
EnableExplicit
 
Macro IsValid(expression)
If expression
PrintN("Valid")
Else
PrintN("Invalid")
EndIf
EndMacro
 
Procedure.i DecodeBase58(Address$, Array result.a(1))
Protected i, j, p
Protected charSet$ = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
Protected c$
 
For i = 1 To Len(Address$)
c$ = Mid(Address$, i, 1)
p = FindString(charSet$, c$) - 1
If p = -1 : ProcedureReturn #False : EndIf; Address contains invalid Base58 character
For j = 24 To 1 Step -1
p + 58 * result(j)
result(j) = p % 256
p / 256
Next j
If p <> 0 : ProcedureReturn #False : EndIf ; Address is too long
Next i
ProcedureReturn #True
EndProcedure
 
Procedure HexToBytes(hex$, Array result.a(1))
Protected i
For i = 1 To Len(hex$) - 1 Step 2
result(i/2) = Val("$" + Mid(hex$, i, 2))
Next
EndProcedure
 
Procedure.i IsBitcoinAddressValid(Address$)
Protected format$, digest$
Protected i, isValid
Protected Dim result.a(24)
Protected Dim result2.a(31)
Protected result$, result2$
; Address length must be between 26 and 35 - see 'https://en.bitcoin.it/wiki/Address'
If Len(Address$) < 26 Or Len(Address$) > 35 : ProcedureReturn #False : EndIf
; and begin with either 1 or 3 which is the format number
format$ = Left(Address$, 1)
If format$ <> "1" And format$ <> "3" : ProcedureReturn #False : EndIf
isValid = DecodeBase58(Address$, result())
If Not isValid : ProcedureReturn #False : EndIf
UseSHA2Fingerprint(); Using functions from PB's built-in Cipher library
digest$ = Fingerprint(@result(), 21, #PB_Cipher_SHA2, 256); apply SHA2-256 to first 21 bytes
HexToBytes(digest$, result2()); change hex string to ascii array
digest$ = Fingerprint(@result2(), 32, #PB_Cipher_SHA2, 256); apply SHA2-256 again to all 32 bytes
HexToBytes(digest$, result2())
result$ = PeekS(@result() + 21, 4, #PB_Ascii); last 4 bytes
result2$ = PeekS(@result2(), 4, #PB_Ascii); first 4 bytes
If result$ <> result2$ : ProcedureReturn #False : EndIf
ProcedureReturn #True
EndProcedure
 
If OpenConsole()
Define address$ = "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i"
Define address2$ = "1BGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i"
Define address3$ = "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I"
Print(address$ + " -> ")
IsValid(IsBitcoinAddressValid(address$))
Print(address2$ + " -> ")
IsValid(IsBitcoinAddressValid(address2$))
Print(address3$ + " -> ")
IsValid(IsBitcoinAddressValid(address3$))
PrintN("")
PrintN("Press any key to close the console")
Repeat: Delay(10) : Until Inkey() <> ""
CloseConsole()
EndIf
 
 
Output:
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i -> Valid
1BGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i -> Invalid
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I -> Invalid

Python[edit]

from hashlib import sha256
 
digits58 = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
 
def decode_base58(bc, length):
n = 0
for char in bc:
n = n * 58 + digits58.index(char)
return n.to_bytes(length, 'big')
def check_bc(bc):
bcbytes = decode_base58(bc, 25)
return bcbytes[-4:] == sha256(sha256(bcbytes[:-4]).digest()).digest()[:4]
 
print(check_bc('1AGNa15ZQXAZUgFiqJ3i7Z2DPU2J6hW62i'))
print(check_bc("17NdbrSGoUotzeGCcMMCqnFkEvLymoou9j"))
Output:

Returns:

False
True
Help
Yuuki-chan edit: Delete this help if it's not needed anymore
For those looking at examples here to try and work out what is required, the n.to_bytes() call is equivalent to this code which converts a (long) integer into individual bytes of a byte array in a particular order:
>>> n = 2491969579123783355964723219455906992268673266682165637887
>>> length = 25
>>> list( reversed(range(length)) )
[24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
>>> assert n.to_bytes(length, 'big') == bytes( (n >> i*8) & 0xff for i in reversed(range(length)))
>>>

Racket[edit]

 
#lang racket/base
 
;; Same sha-256 interface as the same-named task
(require ffi/unsafe ffi/unsafe/define openssl/libcrypto)
(define-ffi-definer defcrypto libcrypto)
(defcrypto SHA256_Init (_fun _pointer -> _int))
(defcrypto SHA256_Update (_fun _pointer _pointer _long -> _int))
(defcrypto SHA256_Final (_fun _pointer _pointer -> _int))
(define (sha256 bytes)
(define ctx (malloc 128))
(define result (make-bytes 32))
(SHA256_Init ctx)
(SHA256_Update ctx bytes (bytes-length bytes))
(SHA256_Final result ctx)
result)
 
;; base58 decoding
(define base58-digits
(let ([v (make-vector 128 #f)])
(for ([i (in-naturals)]
[c "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"])
(vector-set! v (char->integer c) i))
v))
(define (base58->integer str)
(for/fold ([n 0]) ([c str])
(+ (* n 58) (vector-ref base58-digits (char->integer c)))))
 
(define (int->bytes n digits)
(list->bytes (let loop ([n n] [digits digits] [acc '()])
(if (zero? digits) acc
(let-values ([(q r) (quotient/remainder n 256)])
(loop q (sub1 digits) (cons r acc)))))))
 
(define (validate-bitcoin-address str)
(define bs (int->bytes (base58->integer str) 25))
(equal? (subbytes (sha256 (sha256 (subbytes bs 0 21))) 0 4)
(subbytes bs 21)))
 
;; additional tests taken from the other solutions
(validate-bitcoin-address "1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i") ; => #t
(validate-bitcoin-address "1111111111111111111114oLvT2")  ; => #t
(validate-bitcoin-address "17NdbrSGoUotzeGCcMMCqnFkEvLymoou9j") ; => #t
(validate-bitcoin-address "1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9") ; => #t
(validate-bitcoin-address "1badbadbadbadbadbadbadbadbadbadbad") ; => #f
 

Ruby[edit]

 
# Validate Bitcoin address
#
# Nigel_Galloway
# October 13th., 2014
require 'digest/sha2'
def convert g
i,e = '',[]
(0...g.length/2).each{|n| e[n] = g[n+=n]+g[n+1]; i+='H2'}
e.pack(i)
end
N = [0,1,2,3,4,5,6,7,8,nil,nil,nil,nil,nil,nil,nil,9,10,11,12,13,14,15,16,nil,17,18,19,20,21,nil,22,23,24,25,26,27,28,29,30,31,32,nil,nil,nil,nil,nil,nil,33,34,35,36,37,38,39,40,41,42,43,nil,44,45,46,47,48,49,50,51,52,53,54,55,56,57]
A = '1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62x'
g = A.bytes.inject(0){|g,n| g*58+N[n-49]}.to_s(16) # A small and interesting piece of code to do the decoding of base58-encoded data.
n = g.slice!(0..-9)
(n.length...42).each{n.insert(0,'0')}
puts "I think the checksum should be #{g}\nI calculate that it is #{Digest::SHA256.hexdigest(Digest::SHA256.digest(convert(n)))[0,8]}"
 
Output:

With A = '1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i'

I think the checksum should be c046b2ff
I calculate that it is         c046b2ff

With A = '1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62x' (final digit i corrupted to x).

I think the checksum should be c046b30d
I calculate that it is         c046b2ff

Rust[edit]

This requires the rust-crypto crate for sha256.

 
extern crate crypto;
 
use crypto::digest::Digest;
use crypto::sha2::Sha256;
 
const DIGITS58: [char; 58] = ['1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'];
 
fn main() {
println!("{}", validate_address("1AGNa15ZQXAZUgFiqJ3i7Z2DPU2J6hW62i"));
println!("{}", validate_address("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i"));
println!("{}", validate_address("17NdbrSGoUotzeGCcMMCqnFkEvLymoou9j"));
println!("{}", validate_address("17NdbrSGoUotzeGCcMMC?nFkEvLymoou9j"));
}
 
fn validate_address(address: &str) -> bool {
let decoded = match from_base58(address, 25) {
Ok(x) => x,
Err(_) => return false
};
if decoded[0] != 0 {
return false;
}
let mut sha = Sha256::new();
sha.input(&decoded[0..21]);
let mut first_round = vec![0u8; sha.output_bytes()];
sha.result(&mut first_round);
sha.reset();
 
sha.input(&first_round);
let mut second_round = vec![0u8; sha.output_bytes()];
sha.result(&mut second_round);
if second_round[0..4] != decoded[21..25] {
return false
}
true
}
 
fn from_base58(encoded: &str, size: usize) -> Result<Vec<u8>, String> {
let mut res: Vec<u8> = vec![0; size];
for base58_value in encoded.chars() {
let mut value: u32 = match DIGITS58
.iter()
.position(|x| *x == base58_value){
Some(x) => x as u32,
None => return Err(String::from("Invalid character found in encoded string."))
};
for result_index in (0..size).rev() {
value += 58 * res[result_index] as u32;
res[result_index] = (value % 256) as u8;
value /= 256;
}
}
Ok(res)
}
 
Output:
false
true
true
false

Tcl[edit]

Library: Tcllib (Package: sha256)
package require sha256
 
# Generate a large and boring piece of code to do the decoding of
# base58-encoded data.
apply {{} {
set chars "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
set i -1
foreach c [split $chars ""] {
lappend map $c "return -level 0 [incr i]"
}
lappend map default {return -code error "bad character \"$c\""}
proc base58decode str [string map [list @BODY@ [list $map]] {
set num 0
set count [expr {ceil(log(58**[string length $str])/log(256))}]
foreach c [split $str {}] {
set num [expr {$num*58+[switch $c @BODY@]}]
}
for {set i 0} {$i < $count} {incr i} {
append result [binary format c [expr {$num & 255}]]
set num [expr {$num >> 8}]
}
return [string reverse $result]
}]
}}
 
# How to check bitcoin address validity
proc bitcoin_addressValid {address} {
set a [base58decode $address]
set ck [sha2::sha256 -bin [sha2::sha256 -bin [string range $a 0 end-4]]]
if {[string range $a end-3 end] ne [string range $ck 0 3]} {
return -code error "signature does not match"
}
return "$address is ok"
}

Testing if it works

puts [bitcoin_addressValid 1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9]
puts [bitcoin_addressValid 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i]
Output:
1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9 is ok
1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i is ok

UNIX Shell[edit]

Works with: bash
base58=({1..9} {A..H} {J..N} {P..Z} {a..k} {m..z})
bitcoinregex="^[$(printf "%s" "${base58[@]}")]{34}$"
 
decodeBase58() {
local s=$1
for i in {0..57}
do s="${s//${base58[i]}/ $i}"
done
dc <<< "16o0d${s// /+58*}+f"
}
 
checksum() {
xxd -p -r <<<"$1" |
openssl dgst -sha256 -binary |
openssl dgst -sha256 -binary |
xxd -p -c 80 |
head -c 8
}
 
checkBitcoinAddress() {
if [[ "$1" =~ $bitcoinregex ]]
then
h=$(decodeBase58 "$1")
checksum "00${h::${#h}-8}" |
grep -qi "^${h: -8}$"
else return 2
fi
}

zkl[edit]

Uses shared library zklMsgHash.

var [const] MsgHash=Import("zklMsgHash"); // SHA-256, etc
const symbols="123456789" // 58 characters: no cap i,o; ell, zero
"ABCDEFGHJKLMNPQRSTUVWXYZ"
"abcdefghijkmnopqrstuvwxyz";
 
fcn unbase58(str){ // --> Data (byte bucket)
out:=Data().fill(0,25);
str.pump(Void,symbols.index,'wrap(n){ // throws on out of range
[24..0,-1].reduce('wrap(c,idx){
c+=58*out[idx]; // throws if not enough data
out[idx]=c;
c/256; // should be zero when done
},n) : if(_) throw(Exception.ValueError("address too long"));
});
out;
}
 
fcn coinValide(addr){
reg dec,chkSum;
try{ dec=unbase58(addr) }catch{ return(False) }
chkSum=dec[-4,*]; dec.del(21,*);
// hash then hash the hash --> binary hash (instead of hex string)
(2).reduce(MsgHash.SHA256.fp1(1,dec),dec); // dec is i/o buffer
dec[0,4]==chkSum;
}
T("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i","1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9",
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X", // checksum changed, original data.
"1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i", // data changed, original checksum.
"1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i", // invalid chars
"1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz", // too long
).apply(coinValide).println();
Output:
L(True,True,False,False,False,False)