NSData+Base58.h

// Oleg Andreev <[email protected]>

#import <Foundation/Foundation.h>

// Base58 is used for compact human-friendly representation of Bitcoin addresses and private keys.
// Typically Base58-encoded text also contains a checksum.
// Addresses look like 19FGfswVqxNubJbh1NW8A4t51T9x9RDVWQ
// Private keys look like 5KQntKuhYWSRXNqp2yhdXzjekYAR7US3MT1715Mbv5CyUKV6hVe
//
// Here is what Satoshi said about Base58:
// Why base-58 instead of standard base-64 encoding?
// - Don't want 0OIl characters that look the same in some fonts and
//      could be used to create visually identical looking account numbers.
// - A string with non-alphanumeric characters is not as easily accepted as an account number.
// - E-mail usually won't line-break if there's no punctuation to break at.
// - Double-clicking selects the whole number as one word if it's all alphanumeric.

@interface NSString (Base58)

// Returns data for Base58 string without checksum
// Data is mutable so you can clear sensitive information as soon as possible.
- (NSMutableData*) dataFromBase58;

// Returns data for Base58 string with checksum
- (NSMutableData*) dataFromBase58Check;

@end

@interface NSData (Base58)

// String in Base58 without checksum
- (NSString*) base58;

// String in Base58 with checksum
- (NSString*) base58Check;

@end

NSData+Base58.m

// Oleg Andreev <[email protected]>

#import "NSData+Base58.h"
#import "NSData+BTC.h"
#import <openssl/bn.h>

static const char* BTCBase58Alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";

@implementation NSString (Base58)

- (NSMutableData*) dataFromBase58
{
    NSMutableData* result = nil;
    
    BN_CTX* pctx = BN_CTX_new();
    __block BIGNUM bn58; BN_init(&bn58); BN_set_word(&bn58, 58);
    __block BIGNUM bn; BN_init(&bn); BN_zero(&bn);
    __block BIGNUM bnChar; BN_init(&bnChar);
    
    void(^finish)() = ^{
        if (pctx) BN_CTX_free(pctx);
        BN_clear_free(&bn58);
        BN_clear_free(&bn);
        BN_clear_free(&bnChar);
    };
    
    const char* psz = [self cStringUsingEncoding:NSUTF8StringEncoding];
    while (isspace(*psz)) psz++;
    
    
    // Convert big endian string to bignum
    for (const char* p = psz; *p; p++)
    {
        const char* p1 = strchr(BTCBase58Alphabet, *p);
        if (p1 == NULL)
        {
            while (isspace(*p))
                p++;
            if (*p != '\0')
            {
                finish();
                return nil;
            }
            break;
        }
        
        BN_set_word(&bnChar, p1 - BTCBase58Alphabet);
        
        if (!BN_mul(&bn, &bn, &bn58, pctx))
            @throw [NSException exceptionWithName:@"NSString+Base58 Exception"
                                           reason:@"Failed to execute BN_mul." userInfo:nil];
        
        if (!BN_add(&bn, &bn, &bnChar))
            @throw [NSException exceptionWithName:@"NSString+Base58 Exception"
                                           reason:@"Failed to execute BN_add." userInfo:nil];
    }
    
    // Get bignum as little endian data
    
    size_t bnsize = BN_bn2mpi(&bn, NULL);
    if (bnsize <= 4)
    {
        @throw [NSException exceptionWithName:@"NSString+Base58 Exception"
                                       reason:@"Failed to execute BN_bn2mpi." userInfo:nil];
    }
    
    NSMutableData* bndata = [NSMutableData dataWithLength:bnsize];
    BN_bn2mpi(&bn, bndata.mutableBytes);
    [bndata replaceBytesInRange:NSMakeRange(0, 4) withBytes:NULL length:0];
    [bndata reverse];
    
    // Trim off sign byte if present
    bnsize = bndata.length;
    if (bnsize >= 2
        && ((unsigned char*)bndata.bytes)[bnsize - 1] == 0
        && ((unsigned char*)bndata.bytes)[bnsize - 2] >= 0x80)
    {
        bnsize -= 1;
        [bndata setLength:bnsize];
    }
    
    // Restore leading zeros
    int nLeadingZeros = 0;
    for (const char* p = psz; *p == BTCBase58Alphabet[0]; p++)
        nLeadingZeros++;
    
    result = [NSMutableData dataWithLength:nLeadingZeros + bnsize];
    
    // Copy the bignum to the beginning of array. We'll reverse it then and zeros will become leading zeros.
    [result replaceBytesInRange:NSMakeRange(0, bnsize) withBytes:bndata.bytes length:bnsize];
    
    // Convert little endian data to big endian
    [result reverse];
    
    finish();
    
    return result;
}

- (NSMutableData*) dataFromBase58Check
{
    NSMutableData* result = [self dataFromBase58];
    size_t length = result.length;
    if (length < 4)
    {
        return nil;
    }
    NSData* hash = [[result subdataWithRange:NSMakeRange(0, length - 4)] doubleSHA256];
    
    // Last 4 bytes should be equal first 4 bytes of the hash.
    if (memcmp(hash.bytes, result.bytes + length - 4, 4) != 0)
    {
        return nil;
    }
    [result setLength:length - 4];
    return result;
}

@end


@implementation NSData (Base58)

// String in Base58 without checksum
- (NSString*) base58
{
    BN_CTX* pctx = BN_CTX_new();
    __block BIGNUM bn58; BN_init(&bn58); BN_set_word(&bn58, 58);
    __block BIGNUM bn0;  BN_init(&bn0);  BN_zero(&bn0);
    __block BIGNUM bn; BN_init(&bn); BN_zero(&bn);
    __block BIGNUM dv; BN_init(&dv); BN_zero(&dv);
    __block BIGNUM rem; BN_init(&rem); BN_zero(&rem);
    
    void(^finish)() = ^{
        if (pctx) BN_CTX_free(pctx);
        BN_clear_free(&bn58);
        BN_clear_free(&bn0);
        BN_clear_free(&bn);
        BN_clear_free(&dv);
        BN_clear_free(&rem);
    };
    
    // Convert big endian data to little endian.
    // Extra zero at the end make sure bignum will interpret as a positive number.
    NSMutableData* tmp = [self reversedMutableData];
    tmp.length += 1;
    
    // Convert little endian data to bignum
    {
        NSUInteger size = tmp.length;
        NSMutableData* mdata = [tmp mutableCopy];
        // Reverse to convert to OpenSSL bignum endianess
        [mdata reverse];
        // BIGNUM's byte stream format expects 4 bytes of
        // big endian size data info at the front
        [mdata replaceBytesInRange:NSMakeRange(0, 0) withBytes:"\0\0\0\0" length:4];
        unsigned char* bytes = mdata.mutableBytes;
        bytes[0] = (size >> 24) & 0xff;
        bytes[1] = (size >> 16) & 0xff;
        bytes[2] = (size >> 8) & 0xff;
        bytes[3] = (size >> 0) & 0xff;
        
        BN_mpi2bn(bytes, (int)mdata.length, &bn);
    }

    // Expected size increase from base58 conversion is approximately 137%
    // use 138% to be safe
    NSMutableData* stringData = [NSMutableData dataWithCapacity:self.length*138/100 + 1];
    
    while (BN_cmp(&bn, &bn0) > 0)
    {
        if (!BN_div(&dv, &rem, &bn, &bn58, pctx))
        {
            @throw [NSException exceptionWithName:@"NSData+Base58"
                                           reason:@"Failed to execute BN_div." userInfo:nil];
        }
        BN_copy(&bn, &dv);
        unsigned long c = BN_get_word(&rem);
        [stringData appendBytes:BTCBase58Alphabet + c length:1];
    }
    finish();

    // Leading zeroes encoded as base58 ones
    const unsigned char* pbegin = self.bytes;
    const unsigned char* pend = self.bytes + self.length;
    for (const unsigned char* p = pbegin; p < pend && *p == 0; p++)
    {
        [stringData appendBytes:BTCBase58Alphabet + 0 length:1];
    }
    
    // Convert little endian std::string to big endian
    [stringData reverse];
    
    return [[NSString alloc] initWithData:stringData encoding:NSUTF8StringEncoding];
}

// String in Base58 with checksum
- (NSString*) base58Check
{
    // add 4-byte hash check to the end
    NSMutableData* data = [self mutableCopy];
    NSData* checksum = [data doubleSHA256];
    [data appendBytes:checksum.bytes length:4];
    return [data base58];
}

@end

NSData+BTC.h

// Oleg Andreev <[email protected]>

#import <Foundation/Foundation.h>

@interface NSData (BTC)

// Init with securely random byte string from /dev/random
- (id) initRandomWithLength:(NSUInteger)length;

// Init with zero-terminated string in UTF-8 encoding.
- (id) initWithUTF8String:(const char*)utf8string;

// Init with hex string (lower- or uppercase, with optional 0x prefix)
- (id) initWithHexString:(NSString*)hexString;

// Init with zero-terminated hex raw string (lower- or uppercase, with optional 0x prefix)
- (id) initWithHexCString:(const char*)hexCString;

// Returns a copy of data with reversed byte order
- (NSData*) reversedData;
// Returns a reversed mutable copy so you wouldn't need to make another mutable copy
- (NSMutableData*) reversedMutableData;

// Core hash functions that we need
- (NSData*) SHA256;
- (NSData*) RIPEMD160;
- (NSData*) doubleSHA256;    // aka Hash in Bitcoin, more efficient than .SHA256.SHA256
- (NSData*) SHA256RIPEMD160; // aka Hash160 in Bitcoin, more efficient than .SHA256.RIPEMD160

// Formats data as a lowercase hex string
- (NSString*) hexString;
- (NSString*) hexUppercaseString;

// Encrypts/decrypts data using the key. IV is null (you should use random or salted key).
+ (NSMutableData*) encryptData:(NSData*)data key:(NSData*)key;
+ (NSMutableData*) decryptData:(NSData*)data key:(NSData*)key;

@end

@interface NSMutableData (BTC)

// Reversed bytes in place.
- (void) reverse;

// Clears contents of the data to prevent leaks through swapping or buffer-overflow attacks.
- (void) clear;
@end

NSData+BTC.m

// Oleg Andreev <[email protected]>

#import "NSData+BTC.h"
#import <CommonCrypto/CommonCrypto.h>
#include <openssl/ripemd.h>

// This is designed to be not optimized out by compiler like memset
void *NSData_BTCSecureMemset(void *v, int c, size_t n)
{
    if (!v) return v;
    volatile unsigned char *p = v;
    while (n--)
        *p++ = c;
    
    return v;
}

void *NSData_BTCRandomData(size_t length)
{
    FILE *fp = fopen("/dev/random", "r");
    if (!fp)
    {
        NSLog(@"NSData+BTC: cannot fopen /dev/random");
        exit(-1);
        return NULL;
    }
    char* bytes = (char*)malloc(length);
    for (int i = 0; i < length; i++)
    {
        char c = fgetc(fp);
        bytes[i] = c;
    }
    
    fclose(fp);
    return bytes;
}


@implementation NSData (BTC)

- (id) initRandomWithLength:(NSUInteger)length
{
    void *bytes = NSData_BTCRandomData(length);
    if (!bytes) return nil;
    return [self initWithBytesNoCopy:bytes length:length];
}

- (id) initWithUTF8String:(const char*)utf8string
{
    return [self initWithBytes:utf8string length:strlen(utf8string)];
}

- (id) initWithHexString:(NSString*)hexString
{
    return [self initWithHexCString:[hexString cStringUsingEncoding:NSUTF8StringEncoding]];
}

- (id) initWithHexCString:(const char *)hexCString
{
    if (!hexCString) return [self init];

    const unsigned char *psz = (const unsigned char*)hexCString;
    
    while (isspace(*psz)) psz++;
    
    // Skip optional 0x prefix
    if (psz[0] == '0' && tolower(psz[1]) == 'x') psz += 2;
    
    while (isspace(*psz)) psz++;
    
    size_t len = strlen((const char*)psz);

    // If the string is not full number of bytes (each byte 2 hex characters), return nil.
    if (len % 2 != 0) return nil;

    unsigned char* buf = (unsigned char*)malloc(len/2);
    
    static const signed char digits[256] = {
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
         0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
        -1,0xa,0xb,0xc,0xd,0xe,0xf, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1,0xa,0xb,0xc,0xd,0xe,0xf, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
    };
    
    unsigned char* bufpointer = buf;
    
    while (1)
    {
        unsigned char c1 = (unsigned char)*psz++;
        signed char n1 = digits[c1];
        if (n1 == (signed char)-1) break; // break when null-terminator is hit
        
        unsigned char c2 = (unsigned char)*psz++;
        signed char n2 = digits[c2];
        if (n2 == (signed char)-1) break; // break when null-terminator is hit
        
        *bufpointer = (unsigned char)((n1 << 4) | n2);
        bufpointer++;
    }
    
    return [self initWithBytesNoCopy:buf length:len/2];
}

- (NSData*) reversedData
{
    return [self reversedMutableData];
}

- (NSMutableData*) reversedMutableData
{
    NSMutableData* md = [self mutableCopy];
    [md reverse];
    return md;
}

+ (NSMutableData*) encryptData:(NSData*)data key:(NSData*)key
{
    return [self cryptData:data key:key operation:kCCEncrypt];
}

+ (NSMutableData*) decryptData:(NSData*)data key:(NSData*)key
{
    return [self cryptData:data key:key operation:kCCDecrypt];
}

+ (NSMutableData*) cryptData:(NSData*)data key:(NSData*)key operation:(CCOperation)operation
{
    if (!data || !key) return nil;
    
    int encryptedDataCapacity = (int)(data.length / kCCBlockSizeAES128 + 1) * kCCBlockSizeAES128;
    NSMutableData* encryptedData = [[NSMutableData alloc] initWithLength:encryptedDataCapacity];
    
    size_t dataOutMoved = 0;
    CCCryptorStatus cryptstatus = CCCrypt(
      operation,                   // CCOperation op,         /* kCCEncrypt, kCCDecrypt */
      kCCAlgorithmAES128,          // CCAlgorithm alg,        /* kCCAlgorithmAES128, etc. */
      kCCOptionPKCS7Padding,       // CCOptions options,      /* kCCOptionPKCS7Padding, etc. */
      key.bytes,                   // const void *key,
      key.length,                  // size_t keyLength,
      0,                           // const void *iv,         /* optional initialization vector; we'll be using different salt on each login */
      data.bytes,                  // const void *dataIn,     /* optional per op and alg */
      data.length,                 // size_t dataInLength,
      encryptedData.mutableBytes,  // void *dataOut,          /* data RETURNED here */
      encryptedData.length,        // size_t dataOutAvailable,
      &dataOutMoved                // size_t *dataOutMoved
    );
    
    if (cryptstatus == kCCSuccess)
    {
        // Resize the result key to the correct size.
        encryptedData.length = dataOutMoved;
        return encryptedData;
    }
    else
    {
        //kCCSuccess          = 0,
        //kCCParamError       = -4300,
        //kCCBufferTooSmall   = -4301,
        //kCCMemoryFailure    = -4302,
        //kCCAlignmentError   = -4303,
        //kCCDecodeError      = -4304,
        //kCCUnimplemented    = -4305,
        //kCCOverflow         = -4306
        @throw [NSException exceptionWithName:@"NSData+BTC CCCrypt failed"
                                       reason:[NSString stringWithFormat:@"error: %d", cryptstatus] userInfo:nil];
        return nil;
    }
}

- (NSData*) SHA256
{
    unsigned char digest[CC_SHA256_DIGEST_LENGTH];
    CC_SHA256([self bytes], (CC_LONG)[self length], digest);
    return [NSData dataWithBytes:digest length:CC_SHA256_DIGEST_LENGTH];
}

- (NSData*) doubleSHA256
{
    unsigned char digest1[CC_SHA256_DIGEST_LENGTH];
    unsigned char digest2[CC_SHA256_DIGEST_LENGTH];
    CC_SHA256([self bytes], (CC_LONG)[self length], digest1);
    CC_SHA256(digest1, CC_SHA256_DIGEST_LENGTH, digest2);
    return [NSData dataWithBytes:digest2 length:CC_SHA256_DIGEST_LENGTH];
}

- (NSData*) SHA256RIPEMD160
{
    unsigned char digest1[CC_SHA256_DIGEST_LENGTH];
    unsigned char digest2[RIPEMD160_DIGEST_LENGTH];
    CC_SHA256([self bytes], (CC_LONG)[self length], digest1);
    RIPEMD160(digest1, CC_SHA256_DIGEST_LENGTH, digest2);
    return [NSData dataWithBytes:digest2 length:RIPEMD160_DIGEST_LENGTH];
}

- (NSData*) RIPEMD160
{
    unsigned char digest[RIPEMD160_DIGEST_LENGTH];
    RIPEMD160([self bytes], (size_t)[self length], digest);
    return [NSData dataWithBytes:digest length:RIPEMD160_DIGEST_LENGTH];
}

- (NSString*) hexString
{
    return [self hexStringWithFormat:"%02x"];
}

- (NSString*) hexUppercaseString
{
    return [self hexStringWithFormat:"%02X"];
}

- (NSString*) hexStringWithFormat:(const char*)format
{
    if (self.length == 0) return @"";
    
    NSUInteger length = self.length;
    NSMutableData* data = [NSMutableData dataWithLength:length * 2];
    char *dest = data.mutableBytes;
    unsigned const char *src = self.bytes;
    for (int i = 0; i < length; ++i)
    {
        sprintf(dest + i*2, format, (unsigned int)(src[i]));
    }
    return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
}


@end



@implementation NSMutableData (BTC)

- (void) reverse
{
    // K&R
    NSUInteger length = self.length;
    if (length <= 1) return;
    unsigned char* buf = self.mutableBytes;
    unsigned char byte;
    NSUInteger i, j;
    for (i = 0, j = length - 1; i < j; i++, j--)
    {
        byte = buf[i];
        buf[i] = buf[j];
        buf[j] = byte;
    }
}

- (void) clear
{
    [self resetBytesInRange:NSMakeRange(0, self.length)];
}

@end