PyBitmessage/src/addresses.py

import hashlib
from struct import *
from pyelliptic import arithmetic
from binascii import hexlify, unhexlify

#from debug import logger

#There is another copy of this function in Bitmessagemain.py
def convertIntToString(n):
    a = __builtins__.hex(n)
    if a[-1:] == 'L':
        a = a[:-1]
    if (len(a) % 2) == 0:
        return unhexlify(a[2:])
    else:
        return unhexlify('0'+a[2:])

ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"

def encodeBase58(num, alphabet=ALPHABET):
    """Encode a number in Base X

    `num`: The number to encode
    `alphabet`: The alphabet to use for encoding
    """
    if (num == 0):
        return alphabet[0]
    arr = []
    base = len(alphabet)
    while num:
        rem = num % base
        #print 'num is:', num
        num = num // base
        arr.append(alphabet[rem])
    arr.reverse()
    return ''.join(arr)

def decodeBase58(string, alphabet=ALPHABET):
    """Decode a Base X encoded string into the number

    Arguments:
    - `string`: The encoded string
    - `alphabet`: The alphabet to use for encoding
    """
    base = len(alphabet)
    num = 0
    
    try:
        for char in string:
            num *= base
            num += alphabet.index(char)
    except:
        #character not found (like a space character or a 0)
        return 0
    return num

def encodeVarint(integer):
    if integer < 0:
        logger.error('varint cannot be < 0')
        raise SystemExit
    if integer < 253:
        return pack('>B',integer)
    if integer >= 253 and integer < 65536:
        return pack('>B',253) + pack('>H',integer)
    if integer >= 65536 and integer < 4294967296:
        return pack('>B',254) + pack('>I',integer)
    if integer >= 4294967296 and integer < 18446744073709551616:
        return pack('>B',255) + pack('>Q',integer)
    if integer >= 18446744073709551616:
        logger.error('varint cannot be >= 18446744073709551616')
        raise SystemExit
    
class varintDecodeError(Exception):
    pass

def decodeVarint(data):
    """
    Decodes an encoded varint to an integer and returns it. 
    Per protocol v3, the encoded value must be encoded with 
    the minimum amount of data possible or else it is malformed.    
    Returns a tuple: (theEncodedValue, theSizeOfTheVarintInBytes)
    """
    
    if len(data) == 0:
        return (0,0)
    firstByte, = unpack('>B',data[0:1])
    if firstByte < 253:
        # encodes 0 to 252
        return (firstByte,1) #the 1 is the length of the varint
    if firstByte == 253:
        # encodes 253 to 65535
        if len(data) < 3:
            raise varintDecodeError('The first byte of this varint as an integer is %s but the total length is only %s. It needs to be at least 3.' % (firstByte, len(data)))
        encodedValue, = unpack('>H',data[1:3])
        if encodedValue < 253:
            raise varintDecodeError('This varint does not encode the value with the lowest possible number of bytes.')
        return (encodedValue,3)
    if firstByte == 254:
        # encodes 65536 to 4294967295
        if len(data) < 5:
            raise varintDecodeError('The first byte of this varint as an integer is %s but the total length is only %s. It needs to be at least 5.' % (firstByte, len(data)))
        encodedValue, = unpack('>I',data[1:5])
        if encodedValue < 65536:
            raise varintDecodeError('This varint does not encode the value with the lowest possible number of bytes.')
        return (encodedValue,5)
    if firstByte == 255:
        # encodes 4294967296 to 18446744073709551615
        if len(data) < 9:
            raise varintDecodeError('The first byte of this varint as an integer is %s but the total length is only %s. It needs to be at least 9.' % (firstByte, len(data)))
        encodedValue, = unpack('>Q',data[1:9])
        if encodedValue < 4294967296:
            raise varintDecodeError('This varint does not encode the value with the lowest possible number of bytes.')
        return (encodedValue,9)


def calculateInventoryHash(data):
    sha = hashlib.new('sha512')
    sha2 = hashlib.new('sha512')
    sha.update(data)
    sha2.update(sha.digest())
    return sha2.digest()[0:32]

def encodeAddress(version,stream,ripe):
    if version >= 2 and version < 4:
        if len(ripe) != 20:
            raise Exception("Programming error in encodeAddress: The length of a given ripe hash was not 20.")
        if ripe[:2] == '\x00\x00':
            ripe = ripe[2:]
        elif ripe[:1] == '\x00':
            ripe = ripe[1:]
    elif version == 4:
        if len(ripe) != 20:
            raise Exception("Programming error in encodeAddress: The length of a given ripe hash was not 20.")
        ripe = ripe.lstrip('\x00')

    storedBinaryData = encodeVarint(version) + encodeVarint(stream) + ripe
    
    # Generate the checksum
    sha = hashlib.new('sha512')
    sha.update(storedBinaryData)
    currentHash = sha.digest()
    sha = hashlib.new('sha512')
    sha.update(currentHash)
    checksum = sha.digest()[0:4]

    asInt = int(hexlify(storedBinaryData) + hexlify(checksum),16)
    return 'BM-'+ encodeBase58(asInt)

def decodeAddress(address):
    #returns (status, address version number, stream number, data (almost certainly a ripe hash))

    address = str(address).strip()

    if address[:3] == 'BM-':
        integer = decodeBase58(address[3:])
    else:
        integer = decodeBase58(address)
    if integer == 0:
        status = 'invalidcharacters'
        return status,0,0,""
    #after converting to hex, the string will be prepended with a 0x and appended with a L
    hexdata = hex(integer)[2:-1]

    if len(hexdata) % 2 != 0:
        hexdata = '0' + hexdata

    #print 'hexdata', hexdata

    data = unhexlify(hexdata)
    checksum = data[-4:]

    sha = hashlib.new('sha512')
    sha.update(data[:-4])
    currentHash = sha.digest()
    #print 'sha after first hashing: ', sha.hexdigest()
    sha = hashlib.new('sha512')
    sha.update(currentHash)
    #print 'sha after second hashing: ', sha.hexdigest()

    if checksum != sha.digest()[0:4]:
        status = 'checksumfailed'
        return status,0,0,""
    #else:
    #    print 'checksum PASSED'

    try:
        addressVersionNumber, bytesUsedByVersionNumber = decodeVarint(data[:9])
    except varintDecodeError as e:
        logger.error(str(e))
        status = 'varintmalformed'
        return status,0,0,""
    #print 'addressVersionNumber', addressVersionNumber
    #print 'bytesUsedByVersionNumber', bytesUsedByVersionNumber

    if addressVersionNumber > 4:
        logger.error('cannot decode address version numbers this high')
        status = 'versiontoohigh'
        return status,0,0,""
    elif addressVersionNumber == 0:
        logger.error('cannot decode address version numbers of zero.')
        status = 'versiontoohigh'
        return status,0,0,""

    try:
        streamNumber, bytesUsedByStreamNumber = decodeVarint(data[bytesUsedByVersionNumber:])
    except varintDecodeError as e:
        logger.error(str(e))
        status = 'varintmalformed'
        return status,0,0,""
    #print streamNumber
    status = 'success'
    if addressVersionNumber == 1:
        return status,addressVersionNumber,streamNumber,data[-24:-4]
    elif addressVersionNumber == 2 or addressVersionNumber == 3:
        embeddedRipeData = data[bytesUsedByVersionNumber+bytesUsedByStreamNumber:-4]
        if len(embeddedRipeData) == 19:
            return status,addressVersionNumber,streamNumber,'\x00'+embeddedRipeData
        elif len(embeddedRipeData) == 20:
            return status,addressVersionNumber,streamNumber,embeddedRipeData
        elif len(embeddedRipeData) == 18:
            return status,addressVersionNumber,streamNumber,'\x00\x00'+embeddedRipeData
        elif len(embeddedRipeData) < 18:
            return 'ripetooshort',0,0,""
        elif len(embeddedRipeData) > 20:
            return 'ripetoolong',0,0,""
        else:
            return 'otherproblem',0,0,""
    elif addressVersionNumber == 4:
        embeddedRipeData = data[bytesUsedByVersionNumber+bytesUsedByStreamNumber:-4]
        if embeddedRipeData[0:1] == '\x00':
            # In order to enforce address non-malleability, encoded RIPE data must have NULL bytes removed from the front
            return 'encodingproblem',0,0,"" 
        elif len(embeddedRipeData) > 20:
            return 'ripetoolong',0,0,""
        elif len(embeddedRipeData) < 4:
            return 'ripetooshort',0,0,""
        else:
            x00string = '\x00' * (20 - len(embeddedRipeData))
            return status,addressVersionNumber,streamNumber,x00string+embeddedRipeData

def addBMIfNotPresent(address):
    address = str(address).strip()
    if address[:3] != 'BM-':
        return 'BM-'+address
    else:
        return address

if __name__ == "__main__":
    print 'Let us make an address from scratch. Suppose we generate two random 32 byte values and call the first one the signing key and the second one the encryption key:'
    privateSigningKey = '93d0b61371a54b53df143b954035d612f8efa8a3ed1cf842c2186bfd8f876665'
    privateEncryptionKey = '4b0b73a54e19b059dc274ab69df095fe699f43b17397bca26fdf40f4d7400a3a'
    print 'privateSigningKey =', privateSigningKey
    print 'privateEncryptionKey =', privateEncryptionKey
    print 'Now let us convert them to public keys by doing an elliptic curve point multiplication.'
    publicSigningKey = arithmetic.privtopub(privateSigningKey)
    publicEncryptionKey = arithmetic.privtopub(privateEncryptionKey)
    print 'publicSigningKey =', publicSigningKey
    print 'publicEncryptionKey =', publicEncryptionKey

    print 'Notice that they both begin with the \\x04 which specifies the encoding type. This prefix is not send over the wire. You must strip if off before you send your public key across the wire, and you must add it back when you receive a public key.'

    publicSigningKeyBinary = arithmetic.changebase(publicSigningKey,16,256,minlen=64)
    publicEncryptionKeyBinary = arithmetic.changebase(publicEncryptionKey,16,256,minlen=64)

    ripe = hashlib.new('ripemd160')
    sha = hashlib.new('sha512')
    sha.update(publicSigningKeyBinary+publicEncryptionKeyBinary)

    ripe.update(sha.digest())
    addressVersionNumber = 2
    streamNumber = 1
    print 'Ripe digest that we will encode in the address:', hexlify(ripe.digest())
    returnedAddress = encodeAddress(addressVersionNumber,streamNumber,ripe.digest())
    print 'Encoded address:', returnedAddress
    status,addressVersionNumber,streamNumber,data = decodeAddress(returnedAddress)
    print '\nAfter decoding address:'
    print 'Status:', status
    print 'addressVersionNumber', addressVersionNumber
    print 'streamNumber', streamNumber
    print 'length of data(the ripe hash):', len(data)
    print 'ripe data:', hexlify(data)