{"id":12440,"date":"2022-03-02T14:29:00","date_gmt":"2022-03-02T14:29:00","guid":{"rendered":"https:\/\/hederav2stg.wpenginepowered.com\/learning\/understanding-leader-based-consensus-algorithms\/"},"modified":"2025-12-10T16:25:03","modified_gmt":"2025-12-10T16:25:03","slug":"understanding-leader-based-consensus-algorithms","status":"publish","type":"learning","link":"https:\/\/hedera.com\/learning\/understanding-leader-based-consensus-algorithms\/","title":{"rendered":"Understanding leader-based consensus algorithms"},"content":{"rendered":"

Some distributed ledger technologies<\/strong> use leader-based consensus algorithms. Although this consensus mechanism is used in a variety of ways, it presents problems with security and fairness.<\/p>\n

What are leader-based consensus algorithms used for?<\/strong><\/h3>\n

Leader-based consensus algorithms are commonly employed in distributed systems where multiple nodes must agree on a single, consistent state. A typical use case involves transaction ordering in high-throughput environments where concurrent requests for the same resource must be resolved deterministically.<\/p>\n

The consensus mechanism ensures that when multiple clients attempt to access or modify the same data simultaneously, only one request succeeds, preventing conflicts such as double-spending or duplicate resource allocation.<\/p>\n

With a leader-based DLT, the network uses a leader election<\/strong> process to decide on a lead computer or node. Every participant sends its transactions to the leader and then the leader sends out a signal: Here’s the order the transactions need to be in. Or the leader sends out a block that has those transactions in that order, and it’s added to the chain.<\/p>\n

A more traditional consensus mechanism<\/strong> is to use rounds of votes to reach a consensus on how a transaction should be decided, based on Byzantine fault tolerance and the security it provides against malfunctioning Byzantine nodes.<\/p>\n

However leader-based systems, as the name implies, use a leader node or computer to make final decisions on transactions. Proof of work<\/strong>, the backbone of Bitcoin, is an example of a leader-based system.<\/p>\n

Flaws in leader-based consensus algorithms<\/strong><\/h3>\n

The problem with leader-based consensus protocols<\/a> is that they are vulnerable to DDoS attacks<\/strong>. A Distributed Denial of Service attack, in which many computers flood one computer with packets, can crash a leader.<\/p>\n

Of course, leader-based systems are designed so that if the leader goes silent for a certain period of time, the network figures that the leader computer has crashed and switches to a new leader<\/strong>.<\/p>\n

However, if one computer is infected with a virus or a worm, or is malicious or compromised, that one computer will detect the new leader and direct the attack to it. In this way, a botnet can play follow the leader<\/strong> and keep the leader shut down all the time.<\/p>\n

Some systems that don’t appear to be leader based are so \u2013 in effect. They are subject to some of the same problems. In a database, two-phase commit<\/strong> is actually a kind of leader-based system. When a system, such as two-phase commit, has a lock that requires a participant to obtain the lock so it can make a change and then release a lock, that system is leader based.<\/p>\n

If there is a crash<\/strong> while someone is holding the lock, there’s a problem. A DDoS attack can focus on whoever is holding the lock, which causes problems.<\/p>\n

Any system is leader based if the community votes for several leaders to take turns, switching every two seconds. A DDoS can follow the leader with every switch.<\/p>\n

In addition to the security flaws, leader-based consensus algorithms have fairness issues.<\/p>\n

Fairness issues in leader-based systems<\/strong><\/h3>\n

The leader in these distributed systems can control the order <\/strong>in which transactions are placed. So, maybe in a stock market one party bribes the leader to put its transactions ahead of a rival’s. Unethical stock brokers<\/strong> would pay millions of dollars to have that happen even 1 percent of the time.<\/p>\n

Fairness of access<\/strong> is another serious problem. One party could bribe the leader to not even put a rival’s transaction into the block. That second participant would have to wait for a new leader to get access. However, what if several leaders in a row get bribed?<\/p>\n

These consensus algorithms also present concerns over fairness of timestamps<\/strong>. The leader might, through some glitch, put inaccurate timestamps on transactions. A compromised leader might put bad timestamps on transactions on purpose.<\/p>\n

Ideally, the entire community<\/a> puts timestamps on transactions as they are received. They all weigh<\/strong> in and combine to give a single timestamp. Leader-based systems, however, don’t allow that. Typically that all comes down to the leader.<\/p>\n

Putting so much pressure on one point in the network makes leader-based consensus algorithms vulnerable to problems of security and fairness.<\/p>\n","protected":false},"excerpt":{"rendered":"

Some distributed ledger technologies use leader-based consensus algorithms. Although this consensus mechanism is used in a variety of ways, it presents problems with security and fairness. What are leader-based consensus algorithms used for? Leader-based consensus algorithms are commonly employed in distributed systems where multiple nodes must agree on a single, consistent state. A typical use […]<\/p>\n","protected":false},"author":4,"featured_media":0,"template":"","meta":{"_acf_changed":false,"content-type":"","footnotes":""},"tags":[31],"class_list":["post-12440","learning","type-learning","status-publish","hentry","tag-consensus"],"acf":[],"yoast_head":"\nUnderstanding leader-based consensus algorithms | Hedera<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/hedera.com\/learning\/understanding-leader-based-consensus-algorithms\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Understanding leader-based consensus algorithms | Hedera\" \/>\n<meta property=\"og:description\" content=\"Some distributed ledger technologies use leader-based consensus algorithms. 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