Simple, fast, flexible and efficient generation of probably unique identifiers (puid
, aka random strings) of intuitively specified entropy using pre-defined or custom characters.
iex> defmodule(RandId, do: use(Puid, chars: :alpha, total: 1.0e5, risk: 1.0e12))
iex> RandId.generate()
"YAwrpLRqXGlny"
Puid provides a means to create modules for generating random IDs. Specifically, Puid allows full control over all three key characteristics of generating random strings: entropy source, ID characters and ID randomness.
A general overview provides information relevant to the use of Puid for random IDs.
Puid
is used to create individual modules for random ID generation. Creating a random ID generator module is a simple as:
iex> defmodule(SessionId, do: use(Puid))
iex> SessionId.generate()
"8nGA2UaIfaawX-Og61go5A"
The code above use default parameters, so Puid
creates a module suitable for generating session IDs (ID entropy for the default module is 132 bits). Options allow easy and complete control of all three of the important facets of ID generation.
Entropy Source
Puid
uses :crypto.strong_rand_bytes/1 as the default entropy source. The rand_bytes
option can be used to specify any function of the form (non_neg_integer) -> binary
as the source:
iex > defmodule(PrngId, do: use(Puid, rand_bytes: &:rand.bytes/1))
iex> PrngId.generate()
"bIkrSeU6Yr8_1WHGvO0H3M"
Characters
By default, Puid
use the RFC 4648 file system & URL safe characters. The chars
option can by used to specify any of 16 pre-defined character sets or custom characters, including Unicode:
iex> defmodule(HexId, do: use(Puid, chars: :hex))
iex> HexId.generate()
"13fb81e35cb89e5daa5649802ad4bbbd"
iex> defmodule(DingoskyId, do: use(Puid, chars: "dingosky"))
iex> DingoskyId.generate()
"yiidgidnygkgydkodggysonydodndsnkgksgonisnko"
iex> defmodule(DingoskyUnicodeId, do: use(Puid, chars: "dîñgø$kyDÎÑGØßK¥", total: 2.5e6, risk: 1.0e15))
iex> DingoskyUnicodeId.generate()
"øßK$ggKñø$dyGîñdyØøØÎîk"
Captured Entropy
Generated IDs have at least 128-bit entropy by default. Puid
provides a simple, intuitive way to specify ID randomness by declaring a total
number of possible IDs with a specified risk
of a repeat in that many IDs:
To generate up to 10 million random IDs with 1 in a trillion chance of repeat:
iex> defmodule(MyPuid, do: use(Puid, total: 10.0e6, risk: 1.0e15))
iex> MyPuid.generate()
"T0bFZadxBYVKs5lA"
The bits
option can be used to directly specify an amount of ID randomness:
iex> defmodule(Token, do: use(Puid, bits: 256, chars: :hex_upper))
iex> Token.generate()
"6E908C2A1AA7BF101E7041338D43B87266AFA73734F423B6C3C3A17599F40F2A"
Note this is much more intuitive than guess, or simply not knowing, how much entropy your random IDs actually have.
The mathematical approximations used by Puid always favor conservative estimatation:
Add puid
to mix.exs
dependencies:
def deps,
do: [
{:puid, "~> 2.1"}
]
Update dependencies
mix deps.get
Puid
modules have the following functions:
risk
total
puidsbytes
into a puidpuid
into bytesThe total/1
, risk/1
functions provide approximations to the risk of a repeat in some total number of generated puids. The mathematical approximations used purposely overestimate risk and underestimate total.
The encode/1
, decode/1
functions convert String.t()
puids to and from bitstring
bits to facilitate binary data storage, e.g. as an Ecto type.
The info/0
function returns a Puid.Info
structure consisting of:
Puid.Chars
or :custom
bits
since it is a multiple of the entropy bits per
characteriex> defmodule(SafeId, do: use(Puid))
iex> SafeId.generate()
"CSWEPL3AiethdYFlCbSaVC"
iex> SafeId.total(1_000_000)
104350568690606000
iex> SafeId.risk(1.0e12)
9007199254740992
iex> SafeId.decode("CSWEPL3AiethdYFlCbSaVC")
<<9, 37, 132, 60, 189, 192, 137, 235, 97, 117, 129, 101, 9, 180, 154, 84, 32>>
iex> SafeId.encode(<<9, 37, 132, 60, 189, 192, 137, 235, 97, 117, 129, 101, 9, 180, 154, 84, 2::size(4)>>)
"CSWEPL3AiethdYFlCbSaVC"
iex> SafeId.info()
%Puid.Info{
characters: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_",
char_set: :safe64,
entropy_bits: 132.0,
entropy_bits_per_char: 6.0,
ere: 0.75,
length: 22,
rand_bytes: &:crypto.strong_rand_bytes/1
}
There are 19 pre-defined character sets:
Name | Characters |
---|---|
:alpha | ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz |
:alpha_lower | abcdefghijklmnopqrstuvwxyz |
:alpha_upper | ABCDEFGHIJKLMNOPQRSTUVWXYZ |
:alphanum | ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 |
:alphanum_lower | abcdefghijklmnopqrstuvwxyz0123456789 |
:alphanum_upper | ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 |
:base16 | 0123456789ABCDEF |
:base32 | ABCDEFGHIJKLMNOPQRSTUVWXYZ234567 |
:base32_hex | 0123456789abcdefghijklmnopqrstuv |
:base32_hex_upper | 0123456789ABCDEFGHIJKLMNOPQRSTUV |
:crockford32 | 0123456789ABCDEFGHJKMNPQRSTVWXYZ |
:decimal | 0123456789 |
:hex | 0123456789abcdef |
:hex_upper | 0123456789ABCDEF |
:safe_ascii | !#$%&()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_abcdefghijklmnopqrstuvwxyz{|}~ |
:safe32 | 2346789bdfghjmnpqrtBDFGHJLMNPQRT |
:safe64 | ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_ |
:symbol | !#$%&()*+,-./:;<=>?@[]^_{|}~ |
:wordSafe32 | 23456789CFGHJMPQRVWXcfghjmpqrvwx |
Any String
of up to 256 unique characters can be used for puid
generation, with custom characters optimized in the same manner as the pre-defined character sets. The characters must be unique. This isn’t strictly a technical requirement, PUID could handle duplicate characters, but the resulting randomness of the IDs is maximal when the characters are unique, so PUID enforces that restriction.
Name | Description |
---|---|
:base16 | https://datatracker.ietf.org/doc/html/rfc4648#section-8 |
:base32 | https://datatracker.ietf.org/doc/html/rfc4648#section-6 |
:base32_hex | Lowercase of :base32_hex_upper |
:base32_hex_upper | https://datatracker.ietf.org/doc/html/rfc4648#section-7 |
:crockford32 | https://www.crockford.com/base32.html |
:safe_ascii | Printable ascii that does not require escape in String |
:safe32 | Alpha and numbers picked to reduce chance of English words |
:safe64 | https://datatracker.ietf.org/doc/html/rfc4648#section-5 |
:wordSafe32 | Alpha and numbers picked to reduce chance of English words |
Note: :safe32 and :wordSafe32 are two different strategies for the same goal.
As described in the overview, PUID aims to be a general, flexible mechanism for creating random string for use as random IDs. The following comparisons to other Elixir random ID generators is with respect to the issues of random ID generation described in that overview.
PUID is much faster.
Generate 100000 random IDs with 128 bits of entropy using alphanumeric characters
Common Solution (PRNG) : 4.977226
Puid (PRNG) : 0.831748
Common Solution (CSPRNG) : 8.435073
Puid (CSPRNG) : 0.958437
:random.uniform/1
:alphanum
Quite slow compared to PUID
Generate 50000 random IDs with 128 bits of entropy using alphanum characters
Misc.Random (PRNG) : 12.196646
Puid (PRNG) : 0.295741
Misc.Random (CSPRNG) : 11.9858
Puid (CSPRNG) : 0.310417
nanoid is much slower than PUID
Generate 75000 random IDs with 126 bits of entropy using safe64 characters
Nanoid (CSPRNG) : 6.354221
Puid (CSPRNG) : 0.226448
Nanoid (PRNG) : 1.229842
Puid (PRNG) : 0.31025
Generate 75000 random IDs with 195 bits of entropy using alphanum characters
Nanoid (CSPRNG) : 10.295134
Puid (CSPRNG) : 0.809756
Nanoid (PRNG) : 1.678025
Puid (PRNG) : 0.808203
Slower than PUID
Generate 100000 random IDs with 128 bits of entropy using alphanum characters
Randomizer (PRNG) : 1.201281
Puid (PRNG) : 0.829199
Randomizer (CSPRNG) : 4.329881
Puid (CSPRNG) : 0.807226
:crypto.strong_rand_bytes/1
About the same as PUID when using CSPRNG
Generate 500000 random IDs with 128 bits of entropy using hex characters
SecureRandom (CSPRNG) : 1.19713
Puid (CSPRNG) : 1.187726
Generate 500000 random IDs with 128 bits of entropy using safe64 characters
SecureRandom (CSPRNG) : 2.103798
Puid (CSPRNG) : 1.806514
A significant characteristic of ulid is the generation of lexicographically sortable IDs. This is not a goal for PUID; however, one could use PUID to generate such IDs by prefixing a timestamp to a generated puid. Such a solution would be similar to ulid while still providing full control to entropy source, characters, and captured entropy per timestamp context.
ulid and PUID are not directly comparable with regard to speed.
crypto.strong_rand_bytes/1
Similar to PUID when using CSPRNG
Generate 500000 random IDs with 122 bits of entropy using hex
UUID : 1.925131
Puid hex : 1.823116
Generate 500000 random IDs with 122 bits of entropy using safe64
UUID : 1.751625
Puid safe64 : 1.367201