During this summer, I was fortunate to engage in the ‘S** upport for output script descriptors’** project within theBcoinorganization. Participating in the Summer of Bitcoin initiative proved to be a profoundly enriching journey, offering a significant learning curve within the realm of Bitcoin technology. I’d like to express my sincere gratitude to Adi Shankara for expertly guiding this year’s Summer of Bitcoin program. It was indeed a transformative journey.

As I delved further into the intricacies of Bitcoin, I found myself captivated by the remarkable depth of its underlying technology.

Throughout the duration of the project, I had the privilege of working under the guidance of accomplished and fervent experts, namely Matthew Zipkin and Anmol Sharma. Their mentorship not only expanded my knowledge but also played a pivotal role in the successful realization of the project. It is imperative to acknowledge that without their unwavering support, the fruition of this endeavor would have remained unattainable.

What are Descriptors?

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An Output Descriptor is a string of characters in human-readable format that encodes an output script, including all necessary information to solve the script.

You can also think of descriptors as functions. A descriptor returns a script. Some descriptors may incorporate a checksum (part after #) similar to bech32 format, providing an additional layer of error detection to minimize the risk of losing or incorrectly typing characters in the descriptor string when shared with others. We can demonstrate the structure of a descriptor in pseudo code as:

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descriptor_name(argument) => script.

A descriptor wallet is one which stores output descriptors and uses them to create addresses and sign transactions. By abstracting away address creation and transaction signing to a largely standalone module, such wallets can upgrade to using new address types much more easily.
For in depth study on what arguments are allowed inside descriptor and types of descriptors must refer BIP 380** and this doc.

What is the power of Descriptors? Their foremost utility lies in their facilitation of the seamless import and export of seeds and keys, thereby enabling effortless transitions between distinct wallet implementations. They also allow you to build up the precise sort of addresses that you’re interested in creating.

**What changes are being introduced to Bcoin with the implementation of the

Descriptor module?**

Bcoin is** an advanced full node alternative implementation of the Bitcoin protocol, developed using a blend of **JavaScript and C/C++ , specifically designed to operate within the Node.js runtime environment. It boasts comprehensive testing and a profound understanding of all established bitcoin consensus regulations. Moreover, it also functions as a versatile bitcoin library suitable in Node.js environments and web browsers.

The integration of the Descriptor module into Bcoin introduces a pair of novel RPCs: getdescriptorinfo and deriveaddresses. Along with it createmultisig rpc is also redefined with the descriptor functionality.

getdescriptorinfo — This is one of the most important rpc’s which is used for analysing the descriptor. It takes as input a descriptor field and outputs the information regarding the input descriptor along with the checksum.

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{                                   (json object)  
  "descriptor" : "str",             (string) The descriptor in canonical form, without private keys  
  "checksum" : "str",               (string) The checksum for the input descriptor  
  "isrange" : true|false,           (boolean) Whether the descriptor is ranged  
  "issolvable" : true|false,        (boolean) Whether the descriptor is solvable  
  "hasprivatekeys" : true|false     (boolean) Whether the input descriptor contained at least one private key  
}

Source — https://developer.bitcoin.org/reference/rpc/getdescriptorinfo.html

If you seek insight into the implementation details of the getdescriptorinfo RPC within Bcoin, please consult thismerged pr referenced here.

deriveaddresses — Again a very important rpc which is used for deriving addresses the descriptor can produce.

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[           (json array)  
  "str",    (string) the derived addresses  
  ...  
]

Source — __https://developer.bitcoin.org/reference/rpc/deriveaddresses.html

If you seek insight into the implementation details of the deriveaddresses RPC within Bcoin, please consult this**merged pr referenced here.

createmultisig — Used for creating multi-signature address with n signature of m keys required.

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{                            (json object)  
  "address" : "str",         (string) The value of the new multisig address.  
  "redeemScript" : "hex",    (string) The string value of the hex-encoded redemption script.  
  "descriptor" : "str"       (string) The descriptor for this multisig  
}

Source — __https://developer.bitcoin.org/reference/rpc/createmultisig.html

If you seek insight into the implementation details of the createmultisig RPC within Bcoin, please consult this**open prreferenced here.

Overall Learnings and Experience

In conclusion, my journey into the realm of open-source contribution has profoundly transformed my coding approach. Embracing and adhering to the meticulous rules and practices of the organization has instilled a newfound discipline in my coding style. The experience has truly broadened my technical proficiency.

A significant milestone achieved during this journey was conquering my apprehension of version control systems, particularly Git, as I now navigate its functionalities with confidence.

The emphasis on effective communication within the community has proven invaluable, reinforcing the notion that coding is as much about collaboration as it is about individual skill.

This program has provided me with an invaluable opportunity to delve deeper into the intricate world of the Bitcoin rabbit hole, further stoking my curiosity and passion for the technology.

As I reflect on this transformative experience, I am excited about the prospects of continued learning, collaboration, and meaningful contributions in Bitcoin ecosystem.

Thanks for reading!