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3

Indeed hashing is used to ensure integrity, but not this way. What you have in mind it seems is sending (msg, Hash(msg)). Indeed this is not secure because of the attack you describe. The first step starts with something you say by yourself: hashing algorithms are universal algorithms The name is not univesal but public, it means anyone knows it. ...


2

If I understand your question correctly, you want to generate a short value $v(T)$ from a table $T$ such that if $T_1$ and $T_2$ have the same size and the same elements in each corresponding cell, then $v(T_1) = v(T_2)$, and if the tables have different sizes or different elements then $v(T_1) \ne v(T_2)$. What you need for that is two ingredients: A ...


3

You could use a concept similar to the PGP Word List, which attempts to make a binary-representative equivalent of the NATO Phonetic Alphabet, so that fingerprints (bytes) can be expressed vocally in a relatively unambiguous way. Of course, using per-byte words in the case of MD5 means you need 16 words to produce a readable checksum, which may be ...


3

Your math is wrong — not the numerical calculation, but your interpretation of it. There are $256^{17}$ possible inputs and $256^{16}$ possible outputs. On average, there are $256$ inputs for each output. But there are no guarantees that this is the case for all outputs: it's in fact overwhelmingly likely that some outputs have more and others have fewer. ...


0

Of course all the above comments are valid (rogue certificates, fake-websites, ...), but here's another story: Let's assume you to buy, let's say a house. You are lazy and want to sign the contract digitally. The person, selling you the house presents you with a valid certificate and even is so nice to sign the contract you're going to sign. Now you sign ...


0

Since MD5 has been broken, it is technically possible to create arbitrary hashes like the ones you describe above with relative ease. Can you add more context to your question? Do you have the original content that created those hashes?


3

Do you know the article If You’re Typing the Letters A-E-S Into Your Code You’re Doing It Wrong? This is basically the same, but with a focus on hashes. There is a quite important misconception in your system: you stated "One of its design goals was high security." and then you start implementing your selfmade algorithms, even stating: "same key is used ...



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