JCH
Java Community | Help. Code. Learn.•7d ago
dghf

Proper Exception Handling: Try-Catch Blocks with Loops in Cryptographic Hash Collision Program

Hello everyone! I'm working on a cryptographic hashing project where I need to find hash collisions for multiple messages. I'm a bit confused about the proper way to structure my try-catch blocks with loops. Here's my situation: I have an array of messages that I need to process: 
String[] messages = {
    "IV2941 security",
    "Security is fun",
    // ... more messages
};
String[] messages = {
    "IV2941 security",
    "Security is fun",
    // ... more messages
};
I need to hash each message and find collisions, but I'm not sure about the correct way to handle exceptions. Should I: 1. Put the try-catch block inside the for loop: 
for (String message : messages) {
    try {
    MessageDigest md = MessageDigest.getInstance("SHA-256");     // …
    // hash the message, find collisions
    } catch (NoSuchAlgorithmException e) {
        // handle error
    }
}
for (String message : messages) {
    try {
    MessageDigest md = MessageDigest.getInstance("SHA-256");     // …
    // hash the message, find collisions
    } catch (NoSuchAlgorithmException e) {
        // handle error
    }
}
2. Or wrap the entire loop in a try-catch: 
try {
    for (String message : messages) {
         MessageDigest md = MessageDigest.getInstance("SHA-256");         
        // …
        // hash the message, find collisions
    }
} catch (NoSuchAlgorithmException e) {
    // handle error
}
try {
    for (String message : messages) {
         MessageDigest md = MessageDigest.getInstance("SHA-256");         
        // …
        // hash the message, find collisions
    }
} catch (NoSuchAlgorithmException e) {
    // handle error
}
Which approach is better for this kind of cryptographic processing? I want to make sure I'm handling exceptions properly while finding hash collisions. Thanks in advance for any help! 🙏
4 Replies
JavaBot
JavaBot•7d ago
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Hey @dghf! Please use /close or the Close Post button above when your problem is solved. Please remember to follow the help guidelines. This post will be automatically marked as dormant after 300 minutes of inactivity.
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Dioxin
Dioxin•7d ago
depends on what you want to be processed when a failure occurs if you want to stop processing all messages, then it makes sense to keep the loop in the try, so it stops running if an exception is thrown if you want to trigger an error per message, but keep the loop running if an exception occurs, put the try/catch inside the loop
dan1st
dan1st•7d ago
Instead of creating a new MessageDigest in each iteration, you could also create it once outside of the loop and then call reset() after each iteration
JavaBot
JavaBot•7d ago
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