Based on the algorithm as described in https://131002.net/siphash/siphash.pdf, and therefore requires a key alongside the input to use as a seed. This key is required to be 16 bytes, and is measured by Kernel.byte_size/1. An error will be raised if this is not the case. The default implementation is a 2-4 hash, but this can be controlled through the options provided.

Your input must be a binary. It’s possible to add a catch-all to SipHash.hash/3 which simply wraps the input in Kernel.inspect/1, but such usage is not encourage. It’s better to be more explicit about what is being hashed, and Kernel.inspect/1 does not always perform the fastest available conversion (for example, using Poison to encode Maps is far faster, whilst also being more reliable). In addition, the output of Kernel.inspect/1 is specific to Elixir, making it annoyingly unportable.

The current implementation is just a functional hash, with more effort on the code being readable rather than optimized, and as such it’s likely to change in future (if it needs speeding up).

Options

• :case - either of :upper or :lower, defaults to using :upper
• :c and :d - the number of compression rounds, default to 2 and 4
• :padding - when true, pads left with zeroes to 16 chars as necessary

Examples

iex> SipHash.hash("0123456789ABCDEF", "hello")
"3D1974E948748CE2"

iex> SipHash.hash("0123456789ABCDEF", "this is a longer input")
"C7D6D8A1E7D359DD"

iex> SipHash.hash("0123456789ABCDEF", "hello", case: :lower)
"3d1974e948748ce2"

iex> SipHash.hash("0123456789ABCDEF", "zymotechnics", padding: :true)
"09B57037CD3F8F0C"

iex> SipHash.hash("0123456789ABCDEF", "hello", c: 4, d: 8)
"CFFB51E5125013AF"

iex> SipHash.hash("invalid_bytes", "hello")
** (RuntimeError) Key must be exactly 16 bytes.

iex> SipHash.hash("FEDCBA9876543210", %{ "test" => "one" })
** (FunctionClauseError) no function clause matching in SipHash.hash/3

Wrapper around SipHash.hash/3 to rotate the arguments, allowing for more convenient usage when creating a pipeline (you can rotate key/input as needed).

Examples

iex> SipHash.hash_r("hello", "0123456789ABCDEF")
"3D1974E948748CE2"

iex> SipHash.hash_r("this is a longer input", "0123456789ABCDEF")
"C7D6D8A1E7D359DD"

iex> SipHash.hash_r("hello", "0123456789ABCDEF", case: :lower)
"3d1974e948748ce2"

iex> SipHash.hash_r("zymotechnics", "0123456789ABCDEF", padding: :true)
"09B57037CD3F8F0C"

iex> SipHash.hash_r("hello", "invalid_bytes")
** (RuntimeError) Key must be exactly 16 bytes.

iex> SipHash.hash_r(%{ "test" => "one" }, "FEDCBA9876543210")
** (FunctionClauseError) no function clause matching in SipHash.hash/3