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[185.70.43.19]) by gmr-mx.google.com with ESMTPS id 38308e7fff4ca-37e6fe49e2asi1095351fa.1.2025.12.06.08.08.51 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 06 Dec 2025 08:08:51 -0800 (PST) Received-SPF: pass (google.com: domain of uuowwpevskfcordh@proton.me designates 185.70.43.19 as permitted sender) client-ip=185.70.43.19; Date: Sat, 06 Dec 2025 16:08:45 +0000 To: "bitcoindev@googlegroups.com" From: "'uuowwpevskfcordh' via Bitcoin Development Mailing List" Subject: [bitcoindev] Reducing RAM requirements with dynamic dust Message-ID: Feedback-ID: 118992141:user:proton X-Pm-Message-ID: 40a92ad9179e512a3da20029490c1dc18be9cb6e MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="b1=_iDJ3Ii9niVp2TQOoEpcbGZI3SRYrYA9t60QYEzoczDM" X-Original-Sender: uuowwpevskfcordh@proton.me X-Original-Authentication-Results: gmr-mx.google.com; dkim=pass header.i=@proton.me header.s=protonmail header.b=Sw2MlPHa; spf=pass (google.com: domain of uuowwpevskfcordh@proton.me designates 185.70.43.19 as permitted sender) smtp.mailfrom=uuowwpevskfcordh@proton.me; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=proton.me X-Original-From: uuowwpevskfcordh Reply-To: uuowwpevskfcordh Precedence: list Mailing-list: list bitcoindev@googlegroups.com; contact bitcoindev+owners@googlegroups.com List-ID: X-Google-Group-Id: 786775582512 List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , X-Spam-Score: -1.0 (-) --b1=_iDJ3Ii9niVp2TQOoEpcbGZI3SRYrYA9t60QYEzoczDM Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Given the increasing RAM requirements, due to the increasing UTXO set, I su= ggest seeing the UTXO set size as a controlled variable. A feedback mechani= sm sets a dynamic dust level, below from which UTXOs are removed/discarded = and thus freeing RAM. Below is an overview essay better expressed by grok, which can also be seen= in here: https://hackmd.io/P-2lzGb8TiC86IOE3OGiYA?view # Enhancing Bitcoin's Scalability: A PID-Inspired Approach to Managing UTXO= Set Growth ## Abstract Bitcoin=E2=80=99s UTXO set is currently an unbounded accumulator that risks= long-term centralization as node RAM requirements grow without limit. Exis= ting fee incentives have proven insufficient against sustained low-value ou= tput creation (e.g., inscriptions, tokenized assets, dust-heavy protocols).= This article proposes a soft-fork mechanism that treats UTXO set size as a= controlled variable: a slowly rising target size is defined, and a PID-sty= le feedback controller, updated every difficulty epoch, dynamically raises = a minimum-value floor beneath which old UTXOs become unspendable. The resul= t is bounded, predictable growth of the UTXO set with ample warning periods= , no hard caps on monetary use, and strong resistance to bloat attacks=E2= =80=94all while remaining fully compatible with a soft-fork deployment. ## Introduction Bitcoin, the pioneering decentralized digital currency, operates as a compl= ex dynamic system governed by consensus rules that ensure security, immutab= ility, and permissionless participation. At its core, Bitcoin maintains a d= istributed ledger known as the blockchain, which records all transactions i= n a sequence of blocks. Each transaction involves inputs and outputs: input= s reference previously unspent outputs from prior transactions, while outpu= ts create new spendable units called Unspent Transaction Outputs (UTXOs). T= he UTXO set represents the aggregate state of all currently spendable coins= in the network, serving as a critical component for transaction validation= and wallet management. As Bitcoin has evolved, the UTXO set has grown significantly, influenced by= increasing adoption and diverse usage patterns. This growth, while indicat= ive of the network's vitality, poses challenges to its long-term scalabilit= y and decentralization. Nodes=E2=80=94computers that validate and relay tra= nsactions=E2=80=94must store and process the entire UTXO set in memory for = efficient operation, which can strain resources such as random access memor= y (RAM). Unchecked expansion could lead to higher barriers for running full= nodes, potentially centralizing control among fewer, well-resourced partic= ipants. This article explores a proposed mechanism to address these concern= s: an adaptive control system inspired by Proportional-Integral-Derivative = (PID) feedback principles, designed to impose bounded growth on the UTXO se= t while preserving Bitcoin's foundational properties. ## Motivations for UTXO Set Management To appreciate the need for enhanced UTXO management, it is essential to und= erstand the current status quo and its vulnerabilities. Bitcoin's design pr= ioritizes efficiency and security through mechanisms like block size limits= , which cap the amount of data added per block (approximately 1 MB base siz= e, expandable to about 4 MB with Segregated Witness). These limits help con= trol the overall blockchain size, ensuring predictable hardware requirement= s for storage on hard disk drives (HDDs). Similarly, the difficulty adjustm= ent algorithm maintains a consistent block production rate of roughly one e= very 10 minutes by dynamically scaling the computational challenge for mine= rs based on network hashrate. However, the UTXO set lacks comparable built-in constraints. It accumulates= as users create new outputs=E2=80=94often in small denominations=E2=80=94w= ithout a mandatory mechanism to consolidate or prune them. This can result = from various activities, including high-frequency microtransactions, the em= bedding of non-monetary data (such as through protocols like Ordinals, whic= h inscribe arbitrary information onto satoshis, Bitcoin's smallest unit), o= r the anchoring of sidechain or tokenized assets that leverage Bitcoin's se= curity but operate externally. While these innovations expand Bitcoin's uti= lity, they can inadvertently increase the UTXO count disproportionately to = their economic value, elevating transaction fees during congestion and rais= ing operational costs for nodes. Existing incentives, such as transaction fees, partially mitigate this by e= ncouraging users to consolidate low-value UTXOs to avoid higher costs. Yet,= these market-driven forces are insufficient against sustained patterns of = low-value output creation, particularly when driven by external systems tha= t do not bear the full cost of network maintenance. Over time, this leads t= o bloat: as of recent estimates, the UTXO set exceeds several gigabytes whe= n loaded into memory, complicating node synchronization and validation. Wit= hout intervention, projected growth could undermine decentralization, as fe= wer individuals or entities might afford to participate fully in the networ= k. The motivation for reform, therefore, stems from a desire to balance innova= tion with sustainability. An ideal solution would allow gradual UTXO expans= ion to accommodate genuine monetary usage while introducing feedback to cur= b excessive accumulation, all without compromising Bitcoin's permissionless= nature or requiring a hard fork that could fragment the community. ## A PID-Inspired Feedback Controller for UTXO Control Drawing from control theory, which studies how systems maintain desired beh= aviors through feedback, this proposal introduces a dynamic mechanism to re= gulate UTXO set size. PID controllers, widely used in engineering for proce= sses like temperature regulation or autopilot systems, combine three terms:= Proportional \(P\) for immediate response to errors, Integral (I) for corr= ecting persistent deviations, and Derivative (D) for anticipating changes b= ased on trends. In Bitcoin's context, we adapt this framework to compute a = minimum value threshold=E2=80=94or "floor"=E2=80=94below which UTXOs become= ineligible for spending, effectively deprecating them over time. Importantly, this deprecation rule constitutes a soft fork: it restricts th= e set of valid transactions to a subset of those previously allowed, withou= t introducing new capabilities. Upgraded nodes enforce the rule, rejecting = deprecated UTXOs as invalid inputs, ensuring backward compatibility and min= imizing disruption. ### Mechanism Overview The controller activates at each difficulty adjustment epoch, approximately= every two weeks (2016 blocks), aligning with Bitcoin's existing periodic r= ecalibrations for predictability. 1. **Define a Target UTXO Size Trajectory**: Establish an increasing maximu= m target for the UTXO set size, denoted as $T(t)$, where $t$ represents the= epoch number. This could grow sublinearly with time or blockchain height t= o reflect organic adoption=E2=80=94 for instance, $T(t) =3D U_0 \cdot (1 + = r)^t$, with $U_0$ as the initial size and $r$ a small annual growth rate (e= .g., less than 1%). This permits expansion while preventing unbounded diver= gence. 2. **Measure the Error**: At each epoch, compute the error $e(t) =3D S(t) -= T(t)$, where $S(t)$ is the current UTXO set size (measured by count or agg= regate data footprint). 3. **Compute the Floor Adjustment**: Apply the PID formula to adjust the va= lue floor $F(t)$: $$ \Delta F(t) =3D K_p \cdot e(t) + K_i \cdot \sum_{k=3D0}^{t} e(k) + K_d \= cdot \frac{e(t) - e(t-1)}{\Delta t} $$ Here, $K_p, K_i, K_d$ are tunable gains, selected conservatively through si= mulations to ensure stability (e.g., using root locus analysis to avoid osc= illatory or unstable roots in the system's characteristic equation). The fl= oor $F(t)$ increases only if $e(t) > 0$, applying to UTXOs below this thres= hold. 4. **Deprecation Process**: UTXOs with values below $F(t)$ are marked as un= spendable in future transactions. To provide fairness and predictability, i= mplement a grace period (e.g., 4-12 months) during which owners can consoli= date affected UTXOs. 5. **Safeguards and Tuning**: Incorporate clamps on $\Delta F(t)$ (similar = to Bitcoin's difficulty adjustment limits) to prevent abrupt changes that m= ight cause network congestion from mass consolidations. Periodic reviews of= gains and targets via community governance would adapt the system to evolv= ing conditions. ### Stability and Dynamics Considerations In dynamic systems terms, the UTXO set can be modeled as an integrator accu= mulating outputs minus expenditures. The PID controller introduces negative= feedback to dampen this accumulation, driving $S(t)$ toward $T(t)$ with mi= nimal overshoot. Simulations would verify robustness against adversarial sc= enarios, such as deliberate UTXO spam, ensuring the system's poles remain i= n the stable region of the complex plane. Potential benefits include reduced node resource demands, lower fees during= normal operation, and enhanced decentralization. Risks, such as over-depre= cation affecting small holders, can be mitigated through careful gain selec= tion. ## Conclusion This PID-inspired approach offers a principled path to managing Bitcoin's U= TXO set, fostering sustainable growth while upholding core principles. By i= ntegrating feedback control, Bitcoin can evolve as a resilient dynamic syst= em, better equipped for widespread adoption. Further research, including de= tailed modeling and community discourse, is essential to refine and potenti= ally implement such enhancements. --=20 You received this message because you are subscribed to the Google Groups "= Bitcoin Development Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to bitcoindev+unsubscribe@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/= Q4RLVZW6OK88aVcalvUK7KJJIKOXckKhB7a5zTN7LTxA-jzal3587k4yUiIMjcIBoqLI0eK4uQL= ZtjJGsbj1R8zsfaMDM-RGSw2V9KI6AAw%3D%40proton.me. --b1=_iDJ3Ii9niVp2TQOoEpcbGZI3SRYrYA9t60QYEzoczDM Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Given the i= ncreasing RAM requirements, due to the increasing UTXO set, I sug= gest seeing the UTXO set size as a controlled variable. A feedback mechanis= m sets a dynamic dust level, below from which UTXOs are removed/discarded a= nd thus freeing RAM.

Below is an overview essay better expressed by grok, which ca= n also be seen in here:

# Enhancing Bitcoin's Scala= bility: A PID-Inspired Approach to Managing UTXO Set Growth

## Abstract

Bi= tcoin=E2=80=99s UTXO set is currently an unbounded accumulator that risks l= ong-term centralization as node RAM requirements grow without limit. Existi= ng fee incentives have proven insufficient against sustained low-value outp= ut creation (e.g., inscriptions, tokenized assets, dust-heavy protocols). T= his article proposes a soft-fork mechanism that treats UTXO set size as a c= ontrolled variable: a slowly rising target size is defined, and a PID-style= feedback controller, updated every difficulty epoch, dynamically raises a = minimum-value floor beneath which old UTXOs become unspendable. The result = is bounded, predictable growth of the UTXO set with ample warning periods, = no hard caps on monetary use, and strong resistance to bloat attacks=E2=80= =94all while remaining fully compatible with a soft-fork deployment.=

## Introduction

=
Bitcoin, the pioneering decentralized digital currency, operates= as a complex dynamic system governed by consensus rules that ensure securi= ty, immutability, and permissionless participation. At its core, Bitcoin ma= intains a distributed ledger known as the blockchain, which records all tra= nsactions in a sequence of blocks. Each transaction involves inputs and out= puts: inputs reference previously unspent outputs from prior transactions, = while outputs create new spendable units called Unspent Transaction Outputs= (UTXOs). The UTXO set represents the aggregate state of all currently spen= dable coins in the network, serving as a critical component for transaction= validation and wallet management.

As= Bitcoin has evolved, the UTXO set has grown significantly, influenced by i= ncreasing adoption and diverse usage patterns. This growth, while indicativ= e of the network's vitality, poses challenges to its long-term scalability = and decentralization. Nodes=E2=80=94computers that validate and relay trans= actions=E2=80=94must store and process the entire UTXO set in memory for ef= ficient operation, which can strain resources such as random access memory = (RAM). Unchecked expansion could lead to higher barriers for running full n= odes, potentially centralizing control among fewer, well-resourced particip= ants. This article explores a proposed mechanism to address these concerns:= an adaptive control system inspired by Proportional-Integral-Derivative (P= ID) feedback principles, designed to impose bounded growth on the UTXO set = while preserving Bitcoin's foundational properties.

## Motivations for UTXO Set Management

=
To appreciate the need for enhanced UTXO management, it is= essential to understand the current status quo and its vulnerabilities. Bi= tcoin's design prioritizes efficiency and security through mechanisms like = block size limits, which cap the amount of data added per block (approximat= ely 1 MB base size, expandable to about 4 MB with Segregated Witness). Thes= e limits help control the overall blockchain size, ensuring predictable har= dware requirements for storage on hard disk drives (HDDs). Similarly, the d= ifficulty adjustment algorithm maintains a consistent block production rate= of roughly one every 10 minutes by dynamically scaling the computational c= hallenge for miners based on network hashrate.

<= div>However, the UTXO set lacks comparable built-in constraints. It a= ccumulates as users create new outputs=E2=80=94often in small denominations= =E2=80=94without a mandatory mechanism to consolidate or prune them. This c= an result from various activities, including high-frequency microtransactio= ns, the embedding of non-monetary data (such as through protocols like Ordi= nals, which inscribe arbitrary information onto satoshis, Bitcoin's smalles= t unit), or the anchoring of sidechain or tokenized assets that leverage Bi= tcoin's security but operate externally. While these innovations expand Bit= coin's utility, they can inadvertently increase the UTXO count disproportio= nately to their economic value, elevating transaction fees during congestio= n and raising operational costs for nodes.

= Existing incentives, such as transaction fees, partially mitigate thi= s by encouraging users to consolidate low-value UTXOs to avoid higher costs= . Yet, these market-driven forces are insufficient against sustained patter= ns of low-value output creation, particularly when driven by external syste= ms that do not bear the full cost of network maintenance. Over time, this l= eads to bloat: as of recent estimates, the UTXO set exceeds several gigabyt= es when loaded into memory, complicating node synchronization and validatio= n. Without intervention, projected growth could undermine decentralization,= as fewer individuals or entities might afford to participate fully in the = network.

The motivation for reform, t= herefore, stems from a desire to balance innovation with sustainability. An= ideal solution would allow gradual UTXO expansion to accommodate genuine m= onetary usage while introducing feedback to curb excessive accumulation, al= l without compromising Bitcoin's permissionless nature or requiring a hard = fork that could fragment the community.

## A PID-Inspired Feedback Controller for UTXO Control
=
Drawing from control theory, which studies how systems= maintain desired behaviors through feedback, this proposal introduces a dy= namic mechanism to regulate UTXO set size. PID controllers, widely used in = engineering for processes like temperature regulation or autopilot systems,= combine three terms: Proportional \(P\) for immediate response to errors, = Integral (I) for correcting persistent deviations, and Derivative (D) for a= nticipating changes based on trends. In Bitcoin's context, we adapt this fr= amework to compute a minimum value threshold=E2=80=94or "floor"=E2=80=94bel= ow which UTXOs become ineligible for spending, effectively deprecating them= over time.

Importantly, this depreca= tion rule constitutes a soft fork: it restricts the set of valid transactio= ns to a subset of those previously allowed, without introducing new capabil= ities. Upgraded nodes enforce the rule, rejecting deprecated UTXOs as inval= id inputs, ensuring backward compatibility and minimizing disruption.

### Mechanism Overview
The controller activates at each difficulty adjustment e= poch, approximately every two weeks (2016 blocks), aligning with Bitcoin's = existing periodic recalibrations for predictability.

<= /div>
1. **Define a Target UTXO Size Trajectory**: Establish an i= ncreasing maximum target for the UTXO set size, denoted as $T(t)$, where $t= $ represents the epoch number. This could grow sublinearly with time or blo= ckchain height to reflect organic adoption=E2=80=94 for instance, $T(t) =3D= U_0 \cdot (1 + r)^t$, with $U_0$ as the initial size and $r$ a small annua= l growth rate (e.g., less than 1%). This permits expansion while preventing= unbounded divergence.

2. **Measure t= he Error**: At each epoch, compute the error $e(t) =3D S(t) - T(t)$, where = $S(t)$ is the current UTXO set size (measured by count or aggregate data fo= otprint).

3. **Compute the Floor Adju= stment**: Apply the PID formula to adjust the value floor $F(t)$:
   
    $$  \= Delta F(t) =3D K_p \cdot e(t) + K_i \cdot \sum_{k=3D0}^{t} e(k) + K_d \cdot= \frac{e(t) - e(t-1)}{\Delta t} $$
   
   Here, $K_p, K_i, K_d$ are tunable gains, s= elected conservatively through simulations to ensure stability (e.g., using= root locus analysis to avoid oscillatory or unstable roots in the system's= characteristic equation). The floor $F(t)$ increases only if $e(t) > 0$= , applying to UTXOs below this threshold.

<= span>4. **Deprecation Process**: UTXOs with values below $F(t)$ are marked = as unspendable in future transactions. To provide fairness and predictabili= ty, implement a grace period (e.g., 4-12 months) during which owners can co= nsolidate affected UTXOs.

5. **Safegu= ards and Tuning**: Incorporate clamps on $\Delta F(t)$ (similar to Bitcoin'= s difficulty adjustment limits) to prevent abrupt changes that might cause = network congestion from mass consolidations. Periodic reviews of gains and = targets via community governance would adapt the system to evolving conditi= ons.

### Stability and Dynamics Consi= derations

In dynamic systems terms, t= he UTXO set can be modeled as an integrator accumulating outputs minus expe= nditures. The PID controller introduces negative feedback to dampen this ac= cumulation, driving $S(t)$ toward $T(t)$ with minimal overshoot. Simulation= s would verify robustness against adversarial scenarios, such as deliberate= UTXO spam, ensuring the system's poles remain in the stable region of the = complex plane.

Potential benefits inc= lude reduced node resource demands, lower fees during normal operation, and= enhanced decentralization. Risks, such as over-deprecation affecting small= holders, can be mitigated through careful gain selection.

## Conclusion

This P= ID-inspired approach offers a principled path to managing Bitcoin's UTXO se= t, fostering sustainable growth while upholding core principles. By integra= ting feedback control, Bitcoin can evolve as a resilient dynamic system, be= tter equipped for widespread adoption. Further research, including detailed= modeling and community discourse, is essential to refine and potentially i= mplement such enhancements.

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