# Questions tagged [preimage-resistance]

Difficulty of finding an input string that hashes to a given value

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### Example: pre-image resistance to second pre-image resistance

It is possible to convert a pre-image resistant function $f:\{0,1\}^{n}\rightarrow \{0,1\}^{n}$ to a second-preimage resistant function? I am thinking to use a pseudo-random generator and construct ...
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### Hash Function Properties

What I am trying to understand is shown in all three properties of a secure hash function, I will focus on Preimage attack resistance. Preimage resistance: given a hash h, it's difficult to find m s.t....
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### How hard is a known prefix hash preimage attack on SHA-2?

Suppose the attacker knows $X, Z$ such that $H(X || Y) = Z$ If bit-length(Y) < 60 then a brute force attack is possible. What if ...
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### Preimage security of combined hash functions

I am struggling with a property of combined hash function and more precisely concatenation. I have seen that concatenating two collision resistant hash functions preserves this property (same for 2nd ...
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### Changing a bit in IV of MD5

It is obvious that changing even one bit in data or IV (initialization vector) will change the hash value a lot. I want to know if, for example, changing a single bit within the $IV$ in MD5 can be ...
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### Where do hash functions get their preimage resistance?

I read through this answer and it seemed to make sense to me, but when I try to make a simpler answer to explain it to myself I lose something in the process. Here is the much simpler hash function I ...
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### Potential weaknesses when combining hash functions?

For consistency's sake, M is the message, H1 and H2 are separate hash functions. I've heard that concatenation or XORing hash outputs together do not provide improved security against preimage and ...
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### Pre-Image Resistance of repeated, patterned SHA2-256 digests

Suppose $H = \operatorname{SHA2-256}$. Let $H_1 = H(\text{“Alpha1”})$. Let $H_2 = H(\text{“Alpha2”})$. … Let $H_N = H(\text{“AlphaN”})$. So all these digests are based off a common pre-image post-...
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### How to perform Black box testing of a key exchange protocol?

Though obviously not an alternative for proper cryptanalysis, I was wondering about statistical/black box analysis. Should I produce a new key exchange protocol. With the same shape as Diffie-Hellman: ...
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### How to formalize a partial preimage task?

Part of the bitcoin mining proof of work is associated with solving a partial preimage problem. For example, output a preimage message $M′$ which computes to a hash value $Y$ with $|Y| = n$ bits ...
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### Public Key Fingerprint: Preimage Resistance

In my system, “resources” are granted operational certificates signed by a particular CA. Each resource has a unique public/private key pair that it generates once. The operational cert granted by the ...
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### if a hash function has no known preimage attacks, does that mean there are no known attacks against using it in signatures?

Suppose a hash function like SHA-1 has known collision attacks (including chosen-prefix collision attacks) but no known preimage attacks. Does that mean there are no known attacks against using it in ...