12
votes
Accepted
Fast cipher without needing hardware support (like ChaCha20) for disk encryption
Adiantum1 is a wide-block cipher built out of ChaCha12, NH-Poly1305, and—for only a small part of the computation—AES.
Being a wide-block cipher, Adiantum can encrypt, for example, entire 512-byte or ...
9
votes
Accepted
Selection of rotation constants in ARX design
Leaving besides that the designers (NSA) of Simon and Speck did not provide an initial design rational for their ciphers/parameter choices, they added some notes later after pressure from the ...
- 116
8
votes
Weaknesses in ARX block ciphers
What are the weaknesses in a block cipher that uses modular addition, rotations with fixed amounts, and XOR? Can substitution boxes or permutation boxes be replicated with these three operations?
The ...
- 140k
7
votes
Accepted
How are boolean functions used in cryptography?
Many properties of boolean functions are used in stream and block cipher design, e.g., when they are used as filtering and combining functions. Some important examples are:
Nonlinearity (minimal ...
- 20.1k
7
votes
Accepted
ChaCha20 core vs ideal unkeyed PRP
It would be extremily surprising if the ChaCha core was a permutation (as the last P in PRP), although we have no proof it is not (if it was a permutation, it would at least be one we do not known how ...
- 134k
6
votes
Accepted
Converting a 32-bit ARX cipher to a 64-bit one, should the rounds be increased?
Typically when there's a variant of an ARX algorithm that goes from 32-bit words to 64-bit words, we do increase the rounds. As DannyNiu mentioned, BLAKE2 is a variant of ChaCha, and while BLAKE2s (...
- 2,741
4
votes
Weaknesses in ARX block ciphers
You ask "what permutations can you form using those three operations?" The answer was: you can create all permutations by ARX.
However, you can do even better and need only two of them: the XOR is ...
- 41
4
votes
Accepted
How to symmetrically encrypt 64bit values?
Are there any existing algorithms that work for this scenario?
Yes, actually, there are a number of 64 bit block ciphers. The standard wisdom is that they aren't encouraged for general use, ...
- 140k
4
votes
Accepted
Would modifying the key of an arbitrary ARX cipher make it harder to break?
Consider a simple ARX block cipher in which after each block is encrypted, the key is rotated and/or XORed by some variable value
It sounds like you are asking "What if we apply a key schedule at the ...
- 19.4k
4
votes
Achieving non-linearity in a block cipher using only, rotations, shifts, AND, OR, and XOR
The brief answer is: Yes, you can!
You may wish to study NORX, an AEAD scheme submitted to the CAESAR competition, whose essential thesis is that you can simultaneously attain high security, high ...
- 47.2k
3
votes
Weaknesses in ARX block ciphers
One generic weakness of ARX designs is that for certain inputs $x,\ y$, $x + y \equiv x \oplus y$. This allows you to linearize subsections of the state and view them as if addition were not applied ...
- 19.4k
3
votes
Accepted
Role of xor in ARX construction
Xor is the "addition" operator for algebra with boolean operators, while AND is the "multiplication" operator for boolean operators. "Regular" addition and multiplication are the addition/...
- 19.4k
2
votes
Which precautions to protect against side-channel attacks on ARX ciphers?
Side channels
Essentially, side channels tell something about the secret data by using properties (e.g. timing, power consumption) of the algorithm itself. If an algorithm executes in a different way ...
- 1,155
2
votes
Accepted
what are the benefits/limits of constructing AEAD using Duplex mode with ARX primitive (chacha20 for example)?
It is possible!
The SPARKLE suite is a round 2 family of NIST candidates that uses ARX-based permutations to build sponge-based hash functions (called ESCH) and duplex-based AEAD (called Schwaemm): ...
- 456
2
votes
Accepted
Term for non-ARX symmetric-key cryptographic primitive design strategy
Primitives based purely on bitwise and shift/rotate operations can be described as being based on:
Binary Polynomials
Bitwise and, or, not, xor are element-wise $\mathbb{F}_2$ additions and ...
- 8,291
1
vote
Fastest order-sensitive operations
This is one simple idea.
I will use $x_i$ for the vector in $d$ dimensions and use $a_i$ for the corresponding integer
in $\{0,1,\ldots, 2^d-1\}$.
Sort the $a_i$ from small to large. Let $r_i$ be the ...
- 20.1k
1
vote
Accepted
Countermeasures to prevent integral cryptanalysis against 4-rounds AES
This question may be theoretically interesting.
However, it looks to me strongly likely that the nice diffusion properties of AES using operations of order $4$ ShiftRows) and matrix ($4\times 4$) ...
- 20.1k
1
vote
Achieving non-linearity in a block cipher using only, rotations, shifts, AND, OR, and XOR
Notice applying xor against the constant 1 is the not gate. And adding either Or gates or And gates is sufficient to create any function.
Xoring, shift and rotation alone are not sufficient.
- 11.6k
1
vote
Alternative block cipher design paradigms to SP-networks and Feistel-like ones?
Are ARX block ciphers considered there own class of block cipher separate from SPNs and Feistel-like ones?
Generally speaking, yes. ARX ciphers typically only use simple CPU instructions (Addition, ...
- 19.4k
Only top scored, non community-wiki answers of a minimum length are eligible