Cryptographic functions in solidity

Harry Thuku May 3, 2023, 9:29 p.m.

Cryptographic functions play a critical role in the security of blockchain applications. They are used to protect sensitive data, ensure the integrity of transactions, and authenticate users. In Solidity, the programming language used to write smart contracts on the Ethereum blockchain, there are several cryptographic functions that are commonly used. These functions include Keccak256, RIPEMD160, SHA256, and ECRECOVER. In this blog post, we will explore these cryptographic functions in Solidity and how they are used to provide a secure and trustworthy environment for blockchain applications. Whether you are a developer new to Solidity or an experienced blockchain professional, this article will provide valuable insights into the world of cryptography in Solidity.

Cryptographic functions in solidity

The Keccak-256 Function

Keccak-256 is a widely used cryptographic hash function that is implemented in Solidity. It is a member of the Keccak family of hash functions and was selected as the winner of the NIST hash function competition in 2012. This hash function takes an input message of arbitrary length and produces a fixed-size output of 256 bits. This output is commonly referred to as a hash or message digest. The hash function is commonly used to provide a digital fingerprint of an input message. This fingerprint is used for a variety of cryptographic applications, including digital signatures, authentication, and data integrity checking. The output is typically considered to be unique for each input, even if the input differs by only one character. This is what makes the function so useful for creating secure and trustworthy applications. Solidity has built-in support for the Keccak-256 hash function through the "keccak256" function. This function takes a variable length input and returns a 256-bit hash value. Here's an example of how to use the Keccak-256 hash function in Solidity:

                                        
                                            // https://github.com/htostudios/cryptographic-functions.git
pragma solidity ^0.8.0;

contract MyContract {
    function hash(string memory _input) public pure returns(bytes32) {
        return keccak256(abi.encodePacked(_input));
    }
}
                                        
                                    

In this example, we define a function called "hash" that takes a string input and returns a 256-bit hash value using the Keccak-256 hash function. The input string is first encoded using the "abi.encodePacked" function before being passed to the "keccak256" function. This encoding step is necessary because the "keccak256" function only accepts a single argument of type "bytes". Overall, the Keccak-256 hash function is an essential tool in the world of Solidity and blockchain development. It provides a powerful means of ensuring data integrity, authenticity, and security in various cryptographic applications.

RIPEMD160

Another cryptographic hash function that is commonly used in Solidity is RIPEMD160. It is a member of the RIPEMD family of hash functions and produces a fixed-size output of 160 bits. Like other hash functions, RIPEMD160 takes an input message of arbitrary length and produces a unique output that serves as a digital fingerprint of the input message. RIPEMD160 is often used in conjunction with other hash functions such as SHA256 to create a more secure hash value. For example, Bitcoin uses a combination of SHA256 and RIPEMD160 to create unique addresses for users. One advantage of RIPEMD160 is that it is designed to be resistant to various attacks such as collision attacks and preimage attacks. It is also less susceptible to length extension attacks compared to other hash functions such as SHA256. Solidity provides built-in support for the RIPEMD160 hash function through the "ripemd160" function. This function takes a variable length input and returns a 160-bit hash value. Here's an example of how to use the RIPEMD160 hash function in Solidity:

                                        
                                            // https://github.com/htostudios/cryptographic-functions.git
pragma solidity ^0.8.0;

contract MyContract {
    function hash(string memory _input) public pure returns(bytes20) {
        return ripemd160(abi.encodePacked(_input));
    }
}
                                        
                                    

In this example, we define a function called "hash" that takes a string input and returns a 160-bit hash value using the RIPEMD160 hash function. The input string is first encoded using the "abi.encodePacked" function before being passed to the "ripemd160" function. This encoding step is necessary because the "ripemd160" function only accepts a single argument of type "bytes". In conclusion, RIPEMD160 is an important hash function in the world of Solidity and blockchain development. It provides a secure and robust means of creating digital fingerprints of input messages, which is essential for various cryptographic applications such as digital signatures and data integrity checking.

SHA256

SHA256 is a widely used cryptographic hash function that is also commonly implemented in Solidity. It produces a fixed-size output of 256 bits and takes an input message of arbitrary length. Like other hash functions, SHA256 produces a unique output that serves as a digital fingerprint of the input message. The hash function is often used in a variety of cryptographic applications, including digital signatures, authentication, and data integrity checking. It is considered a secure and robust hash function that is resistant to various attacks such as collision attacks, preimage attacks, and birthday attacks. Solidity provides built-in support for the SHA256 hash function through the "sha256" function. This function takes a variable length input and returns a 256-bit hash value. Here's an example of how to use the SHA256 hash function in Solidity:

                                        
                                            // https://github.com/htostudios/cryptographic-functions.git
pragma solidity ^0.8.0;

contract MyContract {
    function hash(string memory _input) public pure returns(bytes32) {
        return sha256(abi.encodePacked(_input));
    }
}
                                        
                                    

In this example, we define a function called "hash" that takes a string input and returns a 256-bit hash value using the SHA256 hash function. The input string is first encoded using the "abi.encodePacked" function before being passed to the "sha256" function. This encoding step is necessary because the "sha256" function only accepts a single argument of type "bytes". Overall, the SHA256 hash function is a critical tool in the world of Solidity and blockchain development. It provides a powerful means of ensuring data integrity, authenticity, and security in various cryptographic applications.

The ecrecover function

In Solidity, ecrecover is a built-in cryptographic function that is used to recover the public key associated with a signed message. It is commonly used in digital signature verification and authentication mechanisms on the Ethereum blockchain. To understand how ecrecover works, it's essential to know that in digital signature schemes, a message is signed using the private key of the signer, and the signature is sent alongside the message to the receiver. The receiver then uses the public key of the signer to verify the signature and authenticate the message. In the case of Ethereum, ecrecover takes four arguments: the hash of the message, the recovery ID (an integer value between 0 and 3), the signature's r-value, and the signature's s-value. The function then recovers the public key associated with the signature, which can be used to verify the signature's authenticity. Here's an example of how to use the ecrecover function in Solidity:

                                        
                                            // https://github.com/htostudios/cryptographic-functions.git
pragma solidity ^0.8.0;

contract MyContract {
    function verify(bytes32 _message, uint8 _v, bytes32 _r, bytes32 _s, address _signer) public pure returns(bool) {
        bytes32 messageHash = keccak256(abi.encodePacked(_message));
        address recoveredAddress = ecrecover(messageHash, _v, _r, _s);
        return recoveredAddress == _signer;
    }
}
                                        
                                    

In this example, we define a function called "verify" that takes four inputs: the hash of the message, the recovery ID, the r-value of the signature, the s-value of the signature, and the address of the signer. The function first computes the hash of the message using the keccak256 function and then calls the ecrecover function with the signature parameters to recover the public key associated with the signature. Finally, the function checks whether the recovered address matches the expected signer's address and returns a Boolean value indicating whether the signature is valid. In conclusion, the ecrecover function is a critical cryptographic function in Solidity and Ethereum blockchain development. It provides a means of verifying digital signatures and authenticating messages sent between parties securely.

In conclusion, cryptographic functions such as Keccak256, RIPEMD160, SHA256, and ecrecover are essential tools in Solidity and Ethereum blockchain development. These functions provide a means of ensuring data integrity, authenticity, and security in various cryptographic applications, including digital signatures, authentication, and data integrity checking. By understanding how these cryptographic functions work and how to use them in Solidity, developers can build more robust and secure smart contracts on the Ethereum blockchain. As the blockchain ecosystem continues to evolve and grow, the importance of cryptographic functions in ensuring the integrity and security of blockchain-based applications will only continue to increase. So, whether you're a seasoned blockchain developer or just getting started, mastering these cryptographic functions will be an essential step in becoming proficient in Solidity and Ethereum blockchain development.