Hi, I’m trying to hash a random number but can’t make it work… num = Enum.random(1..9999) hashed_num = :crypto.hash(:sha256, num) I’m getting “1st argument: not an iodata term” error. From my understanding, Enum.random creates a number and :crypto.hash wants an iodata. The same thing happens if I…

An integer() value is not a subtype of iodata() and even the integers allowed as part of an iolist need to be byte values, so in the range of 0..255. you likely want to encode your integer to a binary format first.

You have to convert the integer to a bitstring then :crypto.hash will accept it: num = 999 width_in_bits = 64 # unsure if it's possible to get this dynamically? bin = <<num::integer-size(width_in_bits)>> hashed_num = :crypto.hash(:sha256, bin) {num, bin, hashed_num} Kernel.SpecialForms —…

num = Enum.random(1..999) |> Integer.to_string() hashed_num = :crypto.hash(:sha256, num) This is the final code for future reference, converting integer to string as @LostKobrakai suggested was all that was needed.

You can transform any term to a binary (and then hash it) with :erlang.binary_to_term/1: iex> :erlang.term_to_binary(42) <<131, 97, 42>> iex> :erlang.term_to_binary(42.0) <<131, 70, 64, 69, 0, 0, 0, 0, 0, 0>> iex> :erlang.term_to_binary({4, 2}) <<131, 104, 2, 97, 4, 97, 2>>

Note that’s hashing the string “999”, not the integer 999, which might make a difference to some intentions or across application contexts. (You could argue that settling on “we always hash everything as utf8-string” as being more transportable/less-complex?) Your hashing here is fixed width but fo…

Not text string. People are telling you to convert your integer to a bit string.

Is this the right way? Enum.random(1..999) |> Integer.to_string() |> Base.encode64()

No, you’re still producing a text string. You were pointed at several other ways above.

[image] soup: if it’s possible to get the bit width of an number dynamically 1..9999 |> Enum.map(&(&1 |> :math.log2() |> ceil))

[image] soup: Smarter than actually not, because I got it wrong. should be log2 |> floor to find the highest bit set.

How to hash a random number?

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Sebb October 23, 2022, 5:59pm 10

1..9999 |> Enum.map(&(&1 |> :math.log2() |> ceil))