1. Registering DKIM Public Key Hashes: Developers can use the contract to register new hashes of DKIM public keys for a domain, so that any email sent from the domain can be verified against the blockchain-stored hash.

2. Validating DKIM Public Key Hashes: The contract allows for the validation of a registered DKIM public key hash. This helps verify if the public key in an email matches the one registered in the blockchain for the domain, confirming the email's authenticity.

3. Revoking Compromised Keys: In the event of a security breach or compromise of a private key, developers can revoke the associated DKIM public key hash to prevent misuse.

For a detailed overview of its functionalities, please refer to the source file: DKIMRegistry.sol

• To Hex String: Convert a uint256 to its ASCII string hexadecimal representation.

string memory hexString = StringUtils.toHexString(12345, 4);
// hexString will be "0x3039" 

• To Hex String Without Prefix: Similar to toHexString but without the "0x" prefix.

string memory hexStringNoPrefix = StringUtils.toHexStringNoPrefix(12345, 4);
// hexStringNoPrefix will be "3039"

• To String from Various Types: Convert uint256, bytes32, or address to a string.

string memory uintToString = StringUtils.toString(uint256(12345));
string memory bytesToString = StringUtils.toString(bytes32("data"));
string memory addressToString = StringUtils.toString(address(0x123));

• String Equality: Check if two strings are equal.

bool isEqual = StringUtils.stringEq("hello", "hello");
// isEqual will be true

• Remove Trailing Zeros: Trims trailing zeros from a string representation of bytes.

string memory trimmedString = StringUtils.removeTrailingZeros("hello\x00\x00");
// trimmedString will be "hello"

• Convert Packed Bytes to String: Unpacks uint256 values into a string, useful for handling compact data representations. 1 packed byte = 31 normal bytes.
• Upper and Lower Case Conversion: Convert a string to all uppercase or lowercase.

string memory upperString = StringUtils.upper("hello"); // "HELLO"
string memory lowerString = StringUtils.lower("HELLO"); // "hello"