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MD5 Hash In Circom In this tutorial, we will implement the MD5 hash in Circom both to compute the hash and to constrain in Circom that it was computed correctly. Although the MD5 hash function is not...
Last updated on Aug 20, 202524 min read
Modeling the Stack Data Structure in ZK This tutorial shows how to create a stack in Circom. Be warned — this chapter is long. However, the strategy for creating ZK proofs about stacks will be...
Last updated on Jan 3, 20263 min read
Quin Selector The Quin Selector is a design pattern that allows us to use a signal as an index for an array of signals. As a prerequisite, we assume the reader has read the chapter on Conditional...
Last updated on Mar 10, 20266 min read
The Permutation Argument A permutation argument is a proof that two lists hold the same elements, but possibly in a different order. For example, is a permutation of and vice-versa. The permutation...
Last updated on Apr 15, 20254 min read
Conditional Statements in Circom Circom is very strict with the usage of if-statements. The following rules must be followed: Signals cannot be used to alter the behavior of an if-statement. A signal...
Last updated on Apr 15, 20258 min read
32-Bit Emulation in ZK The default datatype in ZK is the field element, where all arithmetic is done modulo a large prime number. However, most “real” computation is done using 32, 64, or 256-bit...
Last updated on Aug 20, 2025Introduction to Stateful Computations in ZK When carrying out iterative computations such as powers, factorials, or computing the Fibonacci sequence, we need to “stop the computation” after a certain...
Last updated on Apr 15, 20254 min read
Public and Private Inputs A public input in Circom is a signal in the witness that will be revealed to the verifier. For example, suppose we want to create a ZK proof that states: “we know the input...
Last updated on Apr 15, 202510 min read
Hello World Circom Introduction This chapter shows the relationship between Circom code and the Rank 1 Constraint System (R1CS) it compiles to. Understanding R1CSs is critical to understanding...
Last updated on Aug 20, 20253 min read
Circom Components in a Loop Circom does not allow for components to be directly instantiated in a loop. For example, compiling the following code results in the error below. The workaround is to...
Last updated on Mar 22, 202612 min read
Compute Then Constrain "Compute then constrain" is a design pattern in ZK circuits where an algorithm's correct output is first computed without constraints. The correctness of the solution is then...
Last updated on Aug 20, 20253 min read
Symbolic Variables in Circom A symbolic variable in Circom is a variable that has been assigned values from a signal. When a signal is assigned to a variable (thereby turning it into a symbolic...
Last updated on Apr 15, 2025