散列结果是否与源值相同？ [英] Is a hash result ever the same as the source value?

问题描述

这更像是加密理论的问题，但是哈希算法的结果有可能与源的值相同吗？例如，假设我有一个字符串：

This is more of a cryptography theory question, but is it possible that the result of a hash algorithm will ever be the same value as the source? For example, say I have a string:

baf34551fecb48acc3da868eb85e1b6dac9de356

如果我得到SHA1哈希，结果是：

If I get the SHA1 hash on it, the result is:

4d2f72adbafddfe49a726990a1bcb8d34d3da162

理论上，是否有这两个值匹配的情况？我不是在这里询问SHA1 - 这只是我的例子。我只是想知道如果哈希算法是建立在这样的方式，以防止这种情况。

In theory, is there ever a case where these two values would match? I'm not asking about SHA1 specifically here - it's just my example. I'm just wondering if hashing algorithms are built in such a way as to prevent this.

推荐答案

散列算法 - 但我会惊讶地看到任何明确阻止这一点。毕竟，它真的不重要。

Well, it would depend on the hashing algorithm - but I'd be surprised to see anything explicitly prevent this. After all, it really shouldn't matter.

我怀疑这是不太可能发生，当然（对于加密散列）...但即使它，应该不会导致问题。

I suspect it's very unlikely to happen, of course (for cryptographic hashes)... but even if it does, that shouldn't cause a problem.

对于非加密散列（用于哈希表等），在某些情况下返回源值是完全合理的。例如，在Java中， Integer.hashCode（）只返回嵌入的值。

For non-crypto hashes (used in hash tables etc) it would be perfectly reasonable to return the source value in some cases. For example, in Java, Integer.hashCode() just returns the embedded value.

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