com.sap.cloud.sdk.services.blockchainbusinessservices.blockchainvisibility

Class VisibilityUtils

java.lang.Object

com.sap.cloud.sdk.services.blockchainbusinessservices.blockchainvisibility.VisibilityUtils

@Beta
public class VisibilityUtils
extends Object

This class is trying to help developers to work with MerkleTree class to:
1. Create MerkleTree for given map of key/value pairs
2. Get necessary data as MerkleProof to rebuild the same unique MerkleTree
3. Validate given data against Merkle root

Author:

mehran.shakeri@sap.com

Constructor Summary

Constructors

Constructor and Description
VisibilityUtils()

Method Summary

Modifier and Type	Method and Description
static MerkleTree	buildMerkleTree(LinkedHashMap<String,String> keyValues) Default MessageDigest is set as SHA-256
static MerkleTree	buildMerkleTree(LinkedHashMap<String,String> keyValues, MessageDigest messageDigest) Returns a special MerkleTree serving visibility purpose and efficient in term of storage. First leaf in the result tree is list of all keys in a JSNO format: ["key1","key2"] Rest of the leaves are the values corresponding to the keys in the same order
static MerkleProof	getMerkleProof(MerkleTree tree, Set<Integer> leavesIndexesToShare) Generates and returns necessary information to proof given information are part of the same MerkleTree
static MerkleProof	mergeMerkleProofs(Set<MerkleProof> merkleProofs) Merges a set of MerkleProofs to one MerkleProof.
static boolean	validateMerkleProof(MerkleProof proof, String merkleRootHash) Validates a MerkleProof.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

VisibilityUtils

public VisibilityUtils()

Method Detail

buildMerkleTree

@Nonnull
public static MerkleTree buildMerkleTree(LinkedHashMap<String,String> keyValues)
                                           throws NoSuchAlgorithmException

Default MessageDigest is set as SHA-256

Parameters:

keyValues - LinkedHashMap<String, String> keys can not contain "," character

Returns:

MerkleTree

Throws:

NoSuchAlgorithmException - if the used hashing algorithm is not available

buildMerkleTree

@Nonnull
public static MerkleTree buildMerkleTree(@Nonnull
                                                  LinkedHashMap<String,String> keyValues,
                                                  @Nonnull
                                                  MessageDigest messageDigest)

Returns a special MerkleTree serving visibility purpose and efficient in term of storage.
First leaf in the result tree is list of all keys in a JSNO format: ["key1","key2"]
Rest of the leaves are the values corresponding to the keys in the same order

Parameters:

keyValues - LinkedHashMap<String, String> keys can not contain "," character

messageDigest - message digest to calculate hashing function

Returns:

MerkleTree

getMerkleProof

@Nonnull
public static MerkleProof getMerkleProof(@Nonnull
                                                  MerkleTree tree,
                                                  @Nonnull
                                                  Set<Integer> leavesIndexesToShare)

Generates and returns necessary information to proof given information are part of the same MerkleTree

Parameters:

tree - MerkleTree original Merkle tree

leavesIndexesToShare - List<Integer> list of all leaves indexes we would like to share from the whole tree. Must only contain indexes that exist in the tree.

Returns:

MerkleProof minimum information required to proof shared leaves are part of the same given tree

Throws:

IllegalArgumentException - If leavesIndexesToShare is empty or contains any index that does not exist in the tree.

validateMerkleProof

public static boolean validateMerkleProof(@Nonnull
                                          MerkleProof proof,
                                          @Nonnull
                                          String merkleRootHash)
                                   throws NoSuchAlgorithmException

Validates a MerkleProof.

Parameters:

proof - MerkleProof to validate

merkleRootHash - root hash, which should match the given proof

Returns:

true if the merkleProof matches to the merkleRootHash, false otherwise

Throws:

NoSuchAlgorithmException - If the proof's hashing algorithm is not supported on this system

IllegalArgumentException - If the proof is invalid (does not have a hashing algorithm or has a root hash set)

mergeMerkleProofs

@Nonnull
public static MerkleProof mergeMerkleProofs(@Nonnull
                                                     Set<MerkleProof> merkleProofs)
                                              throws IllegalArgumentException

Merges a set of MerkleProofs to one MerkleProof. All MerkleProofs need to have the same number of leaves and needed to be built with the same hashing algorithm and protocol version.

Parameters:

merkleProofs - set of MerkleProofs

Returns:

MerkleProof

Throws:

IllegalArgumentException - If the Set of Proof are not mergeable.