Questions tagged [rc5]

RC5 is a symmetric key block cipher designed by Ronald Rivest.

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Is it possible to calculate the plaintext length of an RC5-32 encrypted ciphertext?

Calculating the RC5 encrypted size of any data is as simple as rounding up the plaintext length to the nearest multiple of 8. What I'm wondering is whether this can be done in the other direction, to ...
1 vote
1 answer
47 views

Rivest Cipher 6 (RC6) Key Scheduler

I am trying to understand the Key Scheduler used in RC6 and I have a total of 3 questions. The RC6 Wikipedia page says that the only difference between the RC5 and RC6 key scheduler is that more words ...
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Which is best: RC5, RC6, CAST-128, LOKI97, or MARS? [closed]

Considering speed and security, which is best: RC5, RC6, CAST-128, LOKI97, or MARS? What does the scoreboard look like? (I'm asking about the abstract math concept, not related to any code ...
1 vote
1 answer
87 views

Modular Addition in RC5 is linear or not?

So, far my understanding was Modular addition is non linear function which is mainly used in ARX based ciphers. While I was glancing through RC5 paper (https://link.springer.com/content/pdf/10.1007/3-...
4 votes
0 answers
175 views

Breaking RC5 without rotations

I'm trying to follow Schneier's self-study course in cryptanalysis and am ashamed to say I am stuck on the very first problem of breaking 8-round RC5 without any rotations (i.e. just XOR and modular ...
1 vote
1 answer
10k views

Difference between RC2, RC4, RC5 and RC6

Can anyone point out the core differences between these ciphers?
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3 votes
1 answer
132 views

Why is variable rotation uncommon in cryptographic primitives?

Most cryptographic primitives I've seen rotate by a constant. RC5 did something different though: For a word size $w=2^n$, you can take the last $n$ bits of a value as a rotation amount. There's more ...
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2 votes
1 answer
536 views

How to calculate initial RC5 encryption parameters?

I learn from a minithesis to understand RC5. As we can see at the formula, the round 0 must be using A=A+S[0], because the loop is starting at r(round) 1. I tried addition and OR(bitwise) to get the ...
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6 votes
2 answers
6k views

RC2, RC4, RC5 key length

While reading the Wiki page on RC4 I noticed that the key size must be in the range of 40–2,048 bits. So should I understand like this, that I can have a key that has length of, lets say 333 bits? (...