Merkle

Builds a Merkle tree using either sha512, sha256, ripemd160, whirlpool, sha1, md5 or none algorithms.

Usage

Build a Merkle tree

var merkle = require('merkle');
var abcde = ['a', 'b', 'c', 'd', 'e'];

Sync style

var tree = merkle('sha1').sync(abcde);

Async style

merkle('sha1').async(abcde, function(err, tree){
  // ...
});

Stream style

// Stream style -- streams root hash
var merkleStreamRoot = merkle('sha1');
merkleStreamRoot.pipe(process.stdout);

// Stream style -- streams json tree
var es = require('event-stream');
var merkleStreamJson = merkle('sha1').json();
merkleStreamJson
  .pipe(es.stringify())
  .pipe(process.stdout);

abcde.forEach(function(letter){
    merkleStreamJson.write(letter);
});

merkleStreamJson.end();

// out:
// {"root":"114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9","depth":3,"levels":4,"nodes":6}

Working ONLY with lowercase

For historical reasons, hashes were systematically uppercased which could lead to wrong trees (see issue #8).

We've added an extra parameter to avoid this case alteration, so you can work exclusively with lowercase hashes:

var use_uppercase = false;
merkle('sha256', use_uppercase);

We plan to remove this syntax for v1.0.0 and always use lowercase hashes.

Extract tree data

You can get tree root using:

> tree.root();
'114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9'

Get tree depth:

> tree.depth();
3

Get tree number of levels (depth + level of leaves):

> tree.levels();
4

Get tree number of nodes

> tree.nodes();
6

Get a tree level nodes:

> tree.level(0);
['114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9']

> tree.level(1);
[
  '585DD1B0A3A55D9A36DE747EC37524D318E2EBEE',
  '58E6B3A414A1E090DFC6029ADD0F3555CCBA127F'
]

> tree.level(2);
[
  'F4D9EEA3797499E52CC2561F722F935F10365E40',
  '734F7A56211B581395CB40129D307A0717538088',
  '58E6B3A414A1E090DFC6029ADD0F3555CCBA127F'
]

...

Using different hash algorithms

var sha256tree= merkle('sha256').sync(abcde);
var sha1tree  = merkle('sha1').sync(abcde);
var md5tree   = merkle('md5').sync(abcde);
var cleartree = merkle('none').sync(abcde);

> sha256tree.root();
'16E6BEB3E080910740A2923D6091618CAA9968AEAD8A52D187D725D199548E2C'

> sha1tree.root();
'114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9'

> md5tree.root();
'064705BD78652C090975702C9E02E229'

> cleartree.root();
'ABCDE'

Install globally for merkle command

Installing it globally will introduce the merkle command (using sha1 as default):

$ sudo npm install -g merkle
$ merkle a
86F7E437FAA5A7FCE15D1DDCB9EAEAEA377667B8

By default, merkle returns the root of the merkle tree:

$ merkle a b c d e
114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9

But it can be asked for some level:

$ merkle a b c d e -l 0
114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9

$ merkle a b c d e -l 1
585DD1B0A3A55D9A36DE747EC37524D318E2EBEE
58E6B3A414A1E090DFC6029ADD0F3555CCBA127F

Or even all levels:

merkle a b c d e --all
114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9

585DD1B0A3A55D9A36DE747EC37524D318E2EBEE
58E6B3A414A1E090DFC6029ADD0F3555CCBA127F

F4D9EEA3797499E52CC2561F722F935F10365E40
734F7A56211B581395CB40129D307A0717538088
58E6B3A414A1E090DFC6029ADD0F3555CCBA127F

86F7E437FAA5A7FCE15D1DDCB9EAEAEA377667B8
E9D71F5EE7C92D6DC9E92FFDAD17B8BD49418F98
84A516841BA77A5B4648DE2CD0DFCB30EA46DBB4
3C363836CF4E16666669A25DA280A1865C2D2874
58E6B3A414A1E090DFC6029ADD0F3555CCBA127F

You can also change of hash algorithm:

$ merkle a b c d e -h md5
064705BD78652C090975702C9E02E229

$ merkle a b c d e -h clear
ABCDE

And just extract some computation statistics:

$ merkle a b c d e --count
4
=> Total number of levels

$ merkle a b c d e --nodes
6
=> Total number of nodes

Finally, you can ask for help:

$ merkle --help
Build a Merkle Tree and prints its values.
Usage: merkle [leaf...]

Options:
  --version    Prints version
  --help       Prints help
  -l, --level  Prints values of the given level. Defaults to 0 (root).
  -n, --nodes  Prints the number of nodes for the given leaves.
  -c, --count  Prints the number of levels for the given leaves.
  -h, --hash   Hash algorithm to apply on leaves. Values are 'sha1', 'md5' or 'none'.
  -a, --all    Prints all levels of Merkle tree, from leaves to root.
  --level                                                                              [default: 0]
  --hash                                                                               [default: "sha1"]

Concepts

Here is an example of Merkle tree with 5 leaves (taken from Tree Hash EXchange format (THEX)):

                   ROOT=H(H+E)
                    /        \
                   /          \
             H=H(F+G)          E
            /       \           \
           /         \           \
    F=H(A+B)         G=H(C+D)     E
    /     \           /     \      \
   /       \         /       \      \
  A         B       C         D      E


Note: H() is some hash function

Where A,B,C,D,E may be already hashed data. If not, those leaves are turned into hashed data (using either sha1, md5 or clear algorithm).

With such a tree structure, merkle considers the tree has exactly 6 nodes: [ROOT,H,E,F,G,E]. For a given level, nodes are just an array.

Adding a Z value would alter the E branch of the tree:

                    ROOT'=H(H+E')
                    /            \
                   /              \
             H=H(F+G)              E'
            /       \               \
           /         \               \
    F=H(A+B)          G=H(C+D)       E'=H(E+Z)
    /     \           /     \         /     \
   /       \         /       \       /       \
  A         B       C         D     E         Z

ROOT changed to ROOT', E to E', but H did not.

License

This software is provided under MIT license.