The first modification of Merkle Tree existence function
Blockchain Study Notes (2)
Determine whether a certain data is on the tree
How to verify that a certain data is on the tree can be constructed by sorting the hash values when building the tree.
If a certain data is in the leaf, connect the hash value of the corresponding sibling node with its own hash value, and then obtain a new hash value through the hash algorithm, and so on, and finally get a node without siblings The hash value of the point is compared with the root of the tree. If they are the same, it proves that the data exists.
If a certain data is not in the leaf, then by comparing the size of the hash value, and then obtain the hash value of the adjacent two nodes of the hash value corresponding to the data, it proves that the two hash values are adjacent in the tree That's it.
(more eloquent than simple traversal)
The relevant code is implemented as follows:
void tree::buildBaseLeafes(vector<string> base_leafs) //建立叶子节点列表
{
cout << "数据对应的哈希值: " << endl;
for (int i = 0; i < base_leafs.size(); i++) {
cout << base_leafs[i] << " : ";
base_leafs[i] = sha256::hash256_hex_string(base_leafs[i]);
cout << base_leafs[i] << endl;
}
cout << endl << endl;
sort(base_leafs.begin(), base_leafs.end());
cout << "哈希值排序后:" << endl;
for (int i = 0; i < base_leafs.size(); i++) {
cout << base_leafs[i] << endl;
}
cout << endl << endl;
vector<node*> new_nodes;
for (auto leaf : base_leafs) //给每一个字符串创建对应节点，并通过这个字符串设置哈希值
{
node* new_node = new node;
new_node->setHash(leaf);
new_nodes.push_back(new_node);
}
base.push_back(new_nodes);
cout << endl;
}
int tree::verify(string hash)
{
node* el_node = nullptr;
node* el_node_t_1 = nullptr;
node* el_node_t_2 = nullptr;
string act_hash = hash; //想验证的叶子节点的哈希值
int t = 0;
//如果base[0] 即叶子节点中有一个节点的hash值和其相等
for (int i = 0; i < base[0].size(); i++)
{
if (base[0][i]->getHash() == act_hash)
{
el_node = base[0][i];//指向该节点
break;
}
if (i < base[0].size() - 1) {
if (act_hash > base[0][i]->getHash() && act_hash < base[0][i + 1]->getHash()) {
el_node_t_1 = base[0][i];
el_node_t_2 = base[0][i + 1];
t = i;
}
}
}
if (el_node == nullptr)
{
cout << endl;
cout << "使用到的哈希值:" << endl;
cout << endl;
cout << "哈希值相邻的叶子节点:" << endl;
cout << el_node_t_1->getHash() << endl;
cout << el_node_t_2->getHash() << endl;
cout << endl;
if (t % 2 == 0) {
cout << "以上两个哈希值所在节点有同一个父节点..." << endl;
el_node_t_1 = el_node_t_1->getParent();
do {
if (el_node_t_1->checkDir() == 0)
{
std::cout << el_node_t_1->getSibling()->getHash() << endl;
}
else
{
std::cout << el_node_t_1->getSibling()->getHash() << endl;
}
el_node_t_1 = el_node_t_1->getParent();
} while ((el_node_t_1->getParent()) != NULL);
}
else {
cout << "以上两个哈希值所在节点没有相同的父节点..." << endl;
string act_hash_t_1 = el_node_t_1->getHash();
string act_hash_t_2 = el_node_t_2->getHash();
int cor = 0;//判断两个节点是否汇合到同一个父节点
if (el_node_t_1->checkDir() == 0)
{
act_hash_t_1 = sha256::hash256_hex_string(act_hash_t_1 + el_node_t_1->getSibling()->getHash());
}
else
{
act_hash_t_1 = sha256::hash256_hex_string(el_node_t_1->getSibling()->getHash() + act_hash_t_1);
}
if (el_node_t_2->checkDir() == 0)
{
act_hash_t_2 = sha256::hash256_hex_string(act_hash_t_2 + el_node_t_2->getSibling()->getHash());
}
else
{
act_hash_t_2 = sha256::hash256_hex_string(el_node_t_2->getSibling()->getHash() + act_hash_t_2);
}
do {
if (act_hash_t_1 != act_hash_t_2) {
std::cout << el_node_t_1->getSibling()->getHash() << endl;
el_node_t_1 = el_node_t_1->getParent();
std::cout << el_node_t_2->getSibling()->getHash() << endl;
el_node_t_2 = el_node_t_2->getParent();
if (el_node_t_1->checkDir() == 0)
{
act_hash_t_1 = sha256::hash256_hex_string(act_hash_t_1 + el_node_t_1->getSibling()->getHash());
}
else
{
act_hash_t_1 = sha256::hash256_hex_string(el_node_t_1->getSibling()->getHash() + act_hash_t_1);
}
if (el_node_t_2->checkDir() == 0)
{
act_hash_t_2 = sha256::hash256_hex_string(act_hash_t_2 + el_node_t_2->getSibling()->getHash());
}
else
{
act_hash_t_2 = sha256::hash256_hex_string(el_node_t_2->getSibling()->getHash() + act_hash_t_2);
}
}
else {
cor = 1;
el_node_t_1 = el_node_t_1->getParent();
}
} while ((el_node_t_1->getParent()) != NULL && cor == 0);
do {
std::cout << el_node_t_1->getSibling()->getHash() << endl;
el_node_t_1 = el_node_t_1->getParent();
} while ((el_node_t_1->getParent()) != NULL);
}
return 0;
}
else {
cout << "使用到的哈希值:" << endl;
cout << act_hash << endl;
do //验证merkle tree是否改变过
{
//父节点的哈希是左孩子的哈希string+右孩子的哈希string
//如果el_node的父节点的左节点是el_node
if (el_node->checkDir() == 0)
{
//是左孩子就 左孩子的哈希string+右孩子的哈希string
act_hash = sha256::hash256_hex_string(act_hash + el_node->getSibling()->getHash());
}
else
{
act_hash = sha256::hash256_hex_string(el_node->getSibling()->getHash() + act_hash);
}
std::cout << act_hash << endl;
el_node = el_node->getParent();
} while ((el_node->getParent()) != NULL); //到达根节点
return act_hash == merkleRoot ? 1 : 0;
}
}
write at the end
Tip: Please refer to the previous article for the source code: Merkle Tree Construction (C++ Implementation)
This code is for learning reference only. If you have any relevant professional questions, please leave a message in the comment area.