This is my own take for exotic base encodings like Base32, Base58 and Base85. I started to write it in 2013 as coding practice and kept it as a small pet project. I suggest anyone who wants to brush up their coding skills to give those encoding problems a shot. They turned out to be more challenging than I expected. To grasp the algorithms I had to get a pen and paper to see how the math worked.

• Base32: RFC 4648, Crockford, z-base-32, Geohash and Extended Hex (BASE32-HEX) flavors with Crockford character substitution, or any other custom flavors.
• Base58: Bitcoin, Ripple, Flickr and custom flavors.
• Base85: Ascii85, Z85 and custom flavors.
• Base16: UpperCase, LowerCase and ModHex flavors. An experimental hexadecimal encoder/decoder just to see how far I can take the optimizations compared to .NET's implementations. It's quite fast now. It can also be used as a replacement for SoapHexBinary.Parse method since it's missing from .NET Core.
• One-shot memory buffer based APIs for simple use cases.
• Stream-based async APIs for more advanced scenarios.
• Lightweight: No third-party dependencies (depends only on System.Memory package)
• Thread-safe.
• Simple to use.

To install it from NuGet:

Install-Package SimpleBase

Encode a byte array:

using SimpleBase;

byte[] myBuffer;
string result = Base32.Crockford.Encode(myBuffer, padding: true);
// you can also use "ExtendedHex" or "Rfc4648" as encoder flavors

Decode a Base32-encoded string:

using SimpleBase;

string myText = ...
Span<byte> result = Base32.Crockford.Decode(myText);
// Span<byte> is analogous to byte[] in usage but allows the library
// to avoid unnecessary memory copy operations unless needed.
// you can also use "ExtendedHex" or "Rfc4648" as decoder flavors

Encode a byte array:

byte[] myBuffer = ...
string result = Base58.Bitcoin.Encode(myBuffer);
// you can also use "Ripple" or "Flickr" as encoder flavors

Decode a Base58-encoded string:

string myText = ...
Span<byte> result = Base58.Bitcoin.Decode(myText);
// Span<byte> is analogous to byte[] in usage but allows the library
// to avoid unnecessary memory copy operations unless needed.
// you can also use "Ripple" or "Flickr" as decoder flavors

Encode a byte array to Ascii85 string:

byte[] myBuffer = ...
string result = Base85.Ascii85.Encode(myBuffer);
// you can also use Z85 as a flavor

Decode an encoded Ascii85 string:

string encodedString = ...
Span<byte> result = Base85.Ascii85.Decode(encodedString);
// Span<byte> is analogous to byte[] in usage but allows the library
// to avoid unnecessary memory copy operations unless needed.
// you can also use Z85 as a flavor

Both "zero" and "space" shortcuts are supported for Ascii85. Z85 is still vanilla.

Encode a byte array to hex string:

byte[] myBuffer = ...
string result = Base16.EncodeUpper(myBuffer); // encode to uppercase
// or 
string result = Base16.EncodeLower(myBuffer); // encode to lowercase

To decode a valid hex string:

string text = ...
Span<byte> result = Base16.Decode(text); // decodes both upper and lowercase
// Span<byte> is analogous to byte[] in usage but allows the library
// to avoid unnecessary memory copy operations unless needed.

Most encoding classes also support a stream mode that can work on streams, be it a network connection, a file or whatever you want. They are ideal for handling arbitrarily large data as they don't consume memory other than a small buffer when encoding or decoding. Their syntaxes are mostly identical. Text encoding decoding is done through a TextReader/TextWriter and the rest is read through a Stream interface. Here is a simple code that encodes a file to another file using Base85 encoding:

using (var input = File.Open("somefile.bin"))
using (var output = File.Create("somefile.ascii85"))
using (var writer = new TextWriter(output)) // you can specify encoding here
{
  Base85.Ascii85.Encode(input, writer);
}

Decode works similarly. Here is a Base32 file decoder:

using (var input = File.Open("somefile.b32"))
using (var output = File.Create("somefile.bin"))
using (var reader = new TextReader(input)) // specify encoding here
{
	Base32.Crockford.Decode(reader, output);
}

You can also encode/decode streams in asynchronous fashion:

using (var input = File.Open("somefile.bin"))
using (var output = File.Create("somefile.ascii85"))
using (var writer = new TextWriter(output)) // you can specify encoding here
{
  await Base85.Ascii85.EncodeAsync(input, writer);
}

And the decode:

using (var input = File.Open("somefile.b32"))
using (var output = File.Create("somefile.bin"))
using (var reader = new TextReader(input)) // specify encoding here
{
	await Base32.Crockford.DecodeAsync(reader, output);
}

Small buffer sizes are used (64 characters). They are closer to real life applications. Base58 performs really bad in decoding of larger buffer sizes, due to polynomial complexity of numeric base conversions.

64 byte buffer for encoding · 5,000,000 iterations · 80 character string for decoding

I'm sure there are areas for improvement. I didn't want to go further in optimizations which would hurt readability and extensibility. I might experiment on them in the future.

Test suite for Base32 isn't complete, I took most of it from RFC4648. Base58 really lacks a good spec or test vectors needed. I had to resort to using online converters to generate preliminary test vectors.

Base85 tests are also makseshift tests based on what output Cryptii produces. Contribution to missing test cases are greatly appreciated.

It's interesting that I wasn't able to reach .NET Base64's performance with Base16 with a straightforward managed code despite that it's much simpler. I was only able to match it after I converted Base16 to unsafe code with good independent interleaving so CPU pipeline optimizations could take place. Still not satisfied though. Is .NET's Base64 implementation native? Perhaps.

Chatting about this pet project with my friends @detaybey, @vhallac, @alkimake and @Utopians at one of our friend's birthday encouraged me to finish this. Thanks guys. Special thanks to my wife for unlimited tea and love.