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https://github.com/m7a/bo-blake3-ada

BLAKE3 Implementation in Ada
https://github.com/m7a/bo-blake3-ada

ada blake3

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BLAKE3 Implementation in Ada

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README 

        
---

section: 32

x-masysma-name: blake3_ada

title: BLAKE3 Hash Function for Ada

date: 2022/09/13 21:12:43

lang: en-US

author: ["Linux-Fan, Ma_Sys.ma ([email protected])"]

keywords: ["blake3", "hash", "ada", "library"]

x-masysma-version: 1.0.0

x-masysma-website: https://masysma.net/32/blake3_ada.xhtml

x-masysma-repository: https://www.github.com/m7a/bo-blake3-ada

x-masysma-copyright: "2022 Ma_Sys.ma "

---

Abstract

========



This repository provides an Ada implementation of the BLAKE3 Hash Function

reference implementation (cf.

).



This implementation supports hashes and keyed hashes.

It does not currently implement key derivation.



License

=======



Like the reference implementation, this library is available under CC0 and can

hence be freely integrated. See `LICENSE.txt` for details.



Compiling

=========



The following dependencies are required for building:



 * Ada compiler (`gcc`, `gnatmake`)

 * Ant build tool (`ant`)



## Compile



	ant



## Run Tests



	cd test_suite

	ant run



## Install



	install -DsT lib/libblake3.so /usr/local/lib/x86_64-linux-gnu

	install -m 644 -DT lib/blake3.ali /usr/local/lib/x86_64-linux-gnu/ada/adalib/blake3

	install -m 644 -DT lib/blake3.ads /usr/local/share/ada/adainclude/blake3



Repository Structure

====================



This repository contains multiple subdirectories for the various components of

the library.



~~~

/bo-blake3-ada

   |

   +-- lib/

   |    |

   |    +-- blake3.adb                *** This is the implementation. ***

   |    |

   |    +-- blake3.ads                *** Implementation header file. ***

   |    |

   |    +-- build.xml                 Build instructions

   |

   +-- sample/

   |    |

   |    +-- blake3hello.adb           Minimal example program.

   |

   +-- test_suite/                    Test program to process test vectors.

   |

   +-- test_vectors/                  Test vector data and scripts.

   |

   +-- util/

   |    |

   |    +-- blake3ada.adb             Commandline sample application.

   |    |

   |    +-- build.xml                 Build instructions for Linux.

   |

   +-- README.md                      This file.

   |

   +-- LICENSE.txt                    CC0 license.

   |

   +-- build.xml                      Recursive antfile build instructions.

~~~



The important subdirectory regarding the library is `lib`. If you do not

need tests or example programs, it is sufficient to compile and use only the

files from that directory.



Sample Program

==============



This sample program computes the hash over `Hello world.` (hex

`48656c6c6f20776f726c642e0a`). You can find it in directory `sample` under

`blake3hello.adb`.



~~~{.ada}

with Blake3;

with Ada.Text_IO;



procedure Blake3Hello is

	package Output_Formatter is new Ada.Text_IO.Integer_IO(Integer);

 	Ctx: Blake3.Hasher := Blake3.Init;

begin

 	Ctx.Update("Hello world.");

	declare

		Result: constant String := Ctx.Final;

		Hex:    String          := "16#00#";

	begin

		for I in Result'Range loop

			Output_Formatter.Put(Hex, Character'Pos(Result(I)), 16);

			Ada.Text_IO.Put(if Hex(1) = ' ' then ("0" & Hex(5 .. 5))

							else Hex(4 .. 5));

		end loop;

	end;

end Blake3Hello;

~~~



The main complexity of this program arises from the necessity to write the

output. Neither a direct binary output to stdout, nor an easy means to convert

to hexadecimal are available in Ada. As a comparatively short alternative to

using a lookup table, this sample program uses the formatting provided by

Ada.Text_IO.Integer_IO and then postprocesses the output to cut-off any

`16#` leading markers and account for the output right-alignment.



Using the installed Library

===========================



Assuming the library is already installed on your system, you can compile

and run the sample program as follows:



	gnatmake -o blake3hello blake3hello.adb \

		-aO/usr/lib/x86_64-linux-gnu/ada/adalib/blake3 \

		-aI/usr/share/ada/adainclude/blake3 \

		-largs -lblake3

	./blake3hello



Output: `C7A4B65F79934D742EA07A9E85B3BBB1AB9AD9F42033D8A0698495D0F564C804`



Using the Library without Installation

======================================



If the library is not installed on your system, it can be integrated using

multiple different approaches.



## Easy Vendoring



The quickest way to get started is to just include the `blake3.ads` and

`blake3.adb` files into the source tree. Here is what the directory structure

may look like then:



~~~

  ...

   |

   +-- sample/

   |    +-- blake3.adb

   |    +-- blake3.ads

   |    +-- blake3hello.adb

   |    +-- build.xml

  ...

~~~



Compilation and invocation then become trivial:



	cp ../lib/blake3.ad? .

	gnatmake -o blake3hello blake3.adb

	./blake3hello



Output: `C7A4B65F79934D742EA07A9E85B3BBB1AB9AD9F42033D8A0698495D0F564C804`



## Inclusion from different directory



It may not be suitable to just copy-over the files. In this case, it is also

possible to import the compiled library from a different directory. Assume

that the library is compiled but not installed, then the file structure may

look as follows:



~~~

  ...

   +-- lib/

   |    +-- blake3.adb

   |    +-- blake3.ads

   |    +-- blake3.ali

   |    +-- build.xml

   |    +-- libblake3.so

   |

   +-- sample/

   |    +-- blake3hello.adb

   |    +-- build.xml

  ...

~~~



Compilation and invocation then have to account for the library not being

installed as follows:



	gnatmake -o blake3hello blake3hello.adb -aO../lib -aI../lib -largs -lblake3

	LD_LIBRARY_PATH=$PWD/../lib ./blake3hello



Output: `C7A4B65F79934D742EA07A9E85B3BBB1AB9AD9F42033D8A0698495D0F564C804`



API Description

===============



## Types



~~~{.ada}

type    U8     is mod 2**8;

type    U32    is new Interfaces.Unsigned_32;

type    Octets is array (U32 range <>) of U8;

subtype U8x32  is Octets(0..31);

type    Hasher is tagged limited private;

~~~



 * `U8`:     This type is used to represent a single byte.

 * `U32`:    This type is used to represent a 32 bit word.

 * `Octets`: This type is used to represent a byte string.

 * `U8x32`:  This type is used to represent a 32 bytes byte string.

 * `Hasher`: This type is used to represent an opaque context of operation.

 * `String`: Strings are used as an alternative representation of byte strings.

   This allows interfacing with other code without forcing it to use the

   types supplied by this library. Conversion between Octets and Strings can

   be performed by using the `for Octet_Var'Address use String_Var'Address;`

   syntax if necessary.



## Context Re-Use



The `Hasher` contexts provided by this API represent the state of hashing.

Since `Final` does not update the state in any way, it is possible to

call `Final` multiple times without expecting a change in output.



Additionally, it is possible to call `Final`, then perform multiple `Update`

invocations and then call `Final` again. The output of the last `Final`

corresponds to the concatenation of all data supplied through preceding uses

of `Update` on the same context.



It is currently not possible to reset the context to discard the old computation

state. If entirely new data is to be processed, it is suggested to create an

entirely new context for this purpose.



## Functions and Procedures



A detailed description of the API functions follows after the overview excerpt

from `blake3.ads`.



~~~{.ada}

-- Initialize as hash function

function  Init return Hasher;



-- Initialize as keyed hash function

function  Init(Key: in U8x32) return Hasher;

function  Init(Key: in String) return Hasher

				with Pre => Key'Length = Key_Len;



-- Add data to process. Do not call with "empty" Strings

procedure Update(Self: in out Hasher; Input: in String)

				with Pre => Input'Length > 0;

procedure Update(Self: in out Hasher; Input: in Octets);



-- Compute hash, Octets-based API allows variable-length output

function  Final(Self: in Hasher) return String;

procedure Final(Self: in Hasher; Out_Slice: out Octets);

~~~



### `function Init return Hasher`



This function creates a BLAKE3 context to be used as a _hash function_. It has

to be called before using any of the other API functions.



### `function Init(Key: in) return Hasher`



This variant of `Init` creates a BLAKE3 context to be used as a

_keyed hash function_. The user is free to either supply an `U32x8` input

or a 32-byte `String` which the library then interprets as `U32x8` internally

without incurring a notable performance overhead.



### `procedure Update(Self: in out Hasher; Input: in)`



Use this function to supply the data that is considered input into the

(optionally keyed) BLAKE3 hashing function. The user is free to supply the

internal type `Octets` or a regular `String` which the library then interprets

as `Octets` internally.



This API expects the minimum number of bytes supplied to `Update` to be 1.

Do not call it with empty arrays or strings.



### `procedure Final(Self: in Hasher) return String`



This function outputs the 32-byte hash corresponding to the concatenation of all

data supplied with `Update` to the provided `Hasher` context and returns it as

a string with binary data. If this String is to be written to a text format,

a conversion to hexadecimal representation is recommended. See

`util/blake3ada.adb` for an easy means to achieve such a conversion.



### `procedure Final(Self: in Hasher; Out_Slice: out Octets)`



This alternative `Final` implementation uses the internal `Octets` datatype

for output. Additionally, by providing an `Out_Slice` of different length,

different lengths of hashes can be output. Note that BLAKE3 supports arbitrarily

long outputs as needed.



Rationale and Usage Recommendation

==================================



This library was created out of the need to process data from a Rust program

that relies on BLAKE3 for all of its hashing operations. This should not deter

you from using it for creating new hashes in new programs with this library,

too. However, you are advised to also consider chosing a more widely supported

hash function in order to avoid being dependent on a single implementation.



Changes

=======



Feel free to send patches with bugfixes or missing functionality directly to

. Include a note to confirm that you are OK with these

patches being included under CC0. Please note that API breaks are only accepted

if _very strong reasons_ exist to motivate them.