Source

File: wp-includes/formatting.php

function antispambot( $email_address, $hex_encoding = 0 ) {
	$email_no_spam_address = '';
	for ( $i = 0, $len = strlen( $email_address ); $i < $len; $i++ ) {
		$j = rand( 0, 1 + $hex_encoding );
		if ( 0 == $j ) {
			$email_no_spam_address .= '&#' . ord( $email_address[ $i ] ) . ';';
		} elseif ( 1 == $j ) {
			$email_no_spam_address .= $email_address[ $i ];
		} elseif ( 2 == $j ) {
			$email_no_spam_address .= '%' . zeroise( dechex( ord( $email_address[ $i ] ) ), 2 );
		}
	}

	return str_replace( '@', '&#64;', $email_no_spam_address );
}