merkle

Javascript implementation of merkle trees

npm install merkle
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Merkle Build Status

Builds a Merkle tree using either sha1, md5 or clear algorithm.

Usage

Build a Merkle tree

var merkle = require('merkle');

var tree = merkle(['a', 'b', 'c', 'd', 'e'], 'sha1').process();

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 sha1tree  = merkle(['a', 'b', 'c', 'd', 'e'], 'sha1').process();
var md5tree   = merkle(['a', 'b', 'c', 'd', 'e'], 'md5').process();
var cleartree = merkle(['a', 'b', 'c', 'd', 'e'], 'clear').process();

> sha1tree.root();
'114B6E61CB5BB93D862CA3C1DFA8B99E313E66E9'

> md5tree.root();
'064705BD78652C090975702C9E02E229'

> cleartree.root();
'ABCDE'

Install globally for merkle command

Installing it globally will introduce the merkle command:

$ 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.

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