Bitcoin Cash: Tiền mặt điện tử ngang hàng cho thế giới

Abstract

Bitcoin Cash la mot he thong tien mat dien tu ngang hang duoc tach ra tu blockchain Bitcoin vao ngay 1 thang 8 nam 2017. Duoc tao ra de dap ung nhung han che ve kha nang mo rong cua Bitcoin, Bitcoin Cash da tang gioi han kich thuoc block de cho phep thong luong giao dich lon hon va phi thap hon, khoi phuc tam nhin ban dau cua Bitcoin nhu mot phuong tien trao doi thuc te cho cac giao dich hang ngay. Voi cac block 32MB, thuat toan dieu chinh do kho thich ung va su phat trien giao thuc lien tuc, Bitcoin Cash huong toi mo rong on-chain de phuc vu nhu tien mat ngang hang toan cau.

Du an Bitcoin Cash ra doi tu mot bat dong co ban trong cong dong Bitcoin ve cach mang luoi nen mo rong quy mo de dap ung nhu cau ngay cang tang. Trong khi mot phe ung ho cac giai phap mo rong ngoai chuoi nhu Lightning Network duoc xay dung tren Segregated Witness (SegWit), phe con lai lap luan rang viec tang gioi han kich thuoc block la cach tiep can truc tiep va da duoc chung minh nhat de mo rong quy mo. Khi khong the dat duoc dong thuan, nhom sau da thuc hien mot hard fork, tao ra mot chuoi moi bao ton lich su giao dich cua Bitcoin dong thoi ap dung gioi han kich thuoc block lon hon va tu choi SegWit. Tai lieu nay mo ta cac thong so ky thuat, triet ly thiet ke va qua trinh phat trien cua Bitcoin Cash.

Introduction

Whitepaper Bitcoin goc, duoc Satoshi Nakamoto cong bo vao nam 2008, mo ta "mot phien ban tien mat dien tu thuan tuy ngang hang" cho phep "gui thanh toan truc tuyen truc tiep tu mot ben den ben kia ma khong can thong qua mot to chuc tai chinh." Tam nhin nay cua Bitcoin nhu mot phuong tien trao doi cho cac giao dich hang ngay la trung tam cua viec ap dung som va su phat trien cong dong. Nhung nguoi ung ho Bitcoin thoi ky dau thuong de cap den phi giao dich thap va thanh toan nhanh nhu nhung loi the chinh so voi cac he thong tai chinh truyen thong.

Tuy nhien, khi su pho bien cua Bitcoin tang len vao giua nhung nam 2010, mot rang buoc co ban bat dau han che tinh huu ich cua no nhu tien mat dien tu. Gioi han kich thuoc block mot megabyte, ban dau duoc gioi thieu nhu mot bien phap chong spam tam thoi, da tao ra mot tran nhan tao cho so luong giao dich ma mang luoi co the xu ly. Khi nhu cau ve khong gian block tang len, nguoi dung buoc phai canh tranh de co dung luong han che bang cach de xuat phi giao dich cao hon. Den dau nam 2017, phi giao dich Bitcoin trung binh da tang len vai dollar, khien cac giao dich gia tri nho tro nen khong thuc te ve mat kinh te. Trong cac giai doan tac nghen cao diem, phi co the vuot qua hai muoi dollar va cac giao dich co the khong duoc xac nhan trong hang gio hoac tham chi hang ngay.

Tinh huong nay dai dien cho mot su sai lech co ban so voi loi hua ban dau cua Bitcoin. Mot he thong duoc thiet ke de cho phep thanh toan dien tu ngang hang dang tro nen qua dat va qua cham cho chinh nhung truong hop su dung ma no duoc tao ra de phuc vu. Trong khi Bitcoin ngay cang duoc dinh vi la "vang ky thuat so" -- mot phuong tien luu tru gia tri thay vi phuong tien trao doi -- nhieu thanh vien cong dong va nha phat trien tin rang dieu nay dai dien cho su phan boi cac nguyen tac thanh lap cua du an.

Bitcoin Cash duoc tao ra de giai quyet cuoc khung hoang nay bang cach ap dung cach tiep can truc tiep nhat de mo rong quy mo: tang gioi han kich thuoc block. Bang cach cho phep nhieu giao dich hon vua voi moi block, Bitcoin Cash nham khoi phuc phi thap va xac nhan nhanh, lam cho tien mat dien tu ngang hang tro nen thuc te tro lai. Nhung nguoi ung ho du an lap luan rang viec mo rong on-chain khong chi kha thi ve mat ky thuat ma con la cach tiep can ma Satoshi Nakamoto da hinh dung tu dau, chi ra cac thong tin lien lac som trong do Nakamoto da thao luan ve viec tang gioi han kich thuoc block khi mang luoi phat trien.

Viec tao ra Bitcoin Cash vao ngay 1 thang 8 nam 2017 la mot trong nhung su kien quan trong nhat trong lich su tien dien tu. No dai dien cho su chia tach chuoi lon dau tien trong lich su Bitcoin duoc thuc day boi mot bat dong triet hoc thuc su ve huong di tuong lai cua giao thuc. Fork da chung minh rang trong mot he thong phi tap trung, cac tranh chap khong the giai quyet co the duoc giai quyet bang cach cho phep moi phe theo duoi tam nhin cua minh mot cach doc lap, voi thi truong cuoi cung xac dinh ket qua.

Background: The Scaling Debate

Cuoc tranh luan ve mo rong quy mo Bitcoin la mot trong nhung tranh chap gay go va keo dai nhat trong lich su phat trien phan mem ma nguon mo. Ve ban chat, cuoc tranh luan tap trung vao mot cau hoi tuong chung don gian: mang luoi Bitcoin nen tang kha nang xu ly giao dich cua minh nhu the nao? Tuy nhien, cau tra loi cho cau hoi nay da cham den cac van de co ban ve quan tri, phi tap trung, triet ly ky thuat va chinh ban sac cua Bitcoin.

Gioi han kich thuoc block mot megabyte cua Bitcoin duoc Satoshi Nakamoto gioi thieu vao nam 2010 nhu mot bien phap tam thoi de ngan chan cac cuoc tan cong tu choi dich vu trong do mot ke tan cong co the lam ngap mang luoi bang cac block qua lon. Vao thoi diem do, viec su dung block thuc te thap hon nhieu so voi gioi han nay va Nakamoto goi y rang gioi han co the duoc nang len trong tuong lai thong qua mot thay doi don gian trong ma nguon. Tuy nhien, khi viec su dung Bitcoin tang len va cac block bat dau day, viec nang gioi han da tro nen gay tranh cai hon nhieu so voi bat ky ai du doan.

Mot phe, lien quan den doi ngu phat trien Bitcoin Core, lap luan rang kich thuoc block nen giu nho de bao toan tinh phi tap trung. Ly le cua ho la cac block lon hon se tang yeu cau tinh toan va bang thong de chay mot full node, co the loai bo nguoi dung thong thuong va tap trung viec van hanh node vao cac to chuc co nguon luc tot. Ho de xuat mot con duong mo rong thay the: Segregated Witness (SegWit), mot thay doi giao thuc tai cau truc du lieu giao dich de tang hieu qua dung luong giao dich cua block ma khong tang gioi han kich thuoc danh nghia, ket hop voi cac giai phap ngoai chuoi nhu Lightning Network se chuyen hau het cac giao dich ra khoi blockchain chinh.

Phe doi lap, bao gom cac nha phat trien noi bat, tho dao va doanh nghiep, lap luan rang tang gioi han kich thuoc block la giai phap don gian nhat, duoc chung minh nhat va cap bach nhat. Ho cho rang gioi han mot megabyte la mot rang buoc tuy y chua bao gio duoc du dinh la tinh nang vinh vien cua giao thuc, va viec tang phi va tac nghen dang day nguoi dung va thuong nhan ra khoi Bitcoin. Ho hoai nghi ve do phuc tap cua SegWit va lo ngai rang Lightning Network, van con mang tinh ly thuyet lon vao thoi diem do, co the khong bao gio thuc hien duoc loi hua ve cac giao dich re va tuc thi.

Cuoc tranh luan leo thang qua mot loat de xuat va phan de xuat. Bitcoin XT, duoc Mike Hearn va Gavin Andresen de xuat vao nam 2015, tim cach tang kich thuoc block len 8MB. Bitcoin Classic de xuat muc tang khiem ton hon len 2MB. Bitcoin Unlimited de xuat loai bo hoan toan gioi han kich thuoc block, cho phep tho dao tu dat gioi han cua minh thong qua dong luc thi truong. Moi de xuat deu tao ra tranh luan gay gat va khong de xuat nao dat duoc su dong thuan ap dao can thiet cho mot hard fork khong gay tranh cai.

Mot so no luc thoa hiep da duoc thuc hien. Thoa thuan Hong Kong (thang 2 nam 2016) chung kien cac nha phat trien Bitcoin Core va tho dao dong y trien khai SegWit tiep theo la hard fork len 2MB, nhung thoa thuan do gian khi thanh phan hard fork khong duoc theo duoi. Thoa thuan New York (thang 5 nam 2017), con duoc goi la SegWit2x, de xuat kich hoat SegWit ngay lap tuc tiep theo la hard fork 2MB trong vong sau thang. Thoa thuan nay duoc ky boi hon nam muoi cong ty dai dien cho da so hash power cua Bitcoin, nhung no bi phan doi manh me boi doi ngu phat trien Bitcoin Core va mot phan dang ke cua cong dong nguoi dung.

Khi da ro rang rang thoa hiep la bat kha thi, phe block lon quyet dinh hanh dong don phuong. Vao ngay 1 thang 8 nam 2017, ho da thuc hien hard fork blockchain Bitcoin, tao ra Bitcoin Cash voi gioi han kich thuoc block ban dau la 8MB. Day khong phai la mot quyet dinh duoc dua ra mot cach nhe nhang -- no doi hoi phai chia tach blockchain, mang luoi, cong dong va thuong hieu. Nhung nhung nguoi ung ho Bitcoin Cash tin rang do la cach duy nhat de bao ton tam nhin ban dau cua Bitcoin nhu tien mat dien tu ngang hang.

The Fork

Hard fork Bitcoin Cash duoc thuc hien vao ngay 1 thang 8 nam 2017 tai do cao block 478.558. Tai thoi diem do, blockchain Bitcoin tach thanh hai chuoi rieng biet: chuoi goc tiep tuc la Bitcoin (BTC) voi viec kich hoat SegWit, va chuoi moi tro thanh Bitcoin Cash (BCH) voi gioi han kich thuoc block tang len 8MB.

Fork duoc thuc hien sach se ve mat ky thuat va duoc len ke hoach tot. Moi dia chi Bitcoin co so du tai thoi diem fork deu nhan duoc so du tuong tu tren ca hai chuoi. Neu mot nguoi dung co 1 BTC truoc fork, ho se co 1 BTC tren chuoi Bitcoin va 1 BCH tren chuoi Bitcoin Cash sau fork. Toan bo lich su giao dich truoc block 478.558 duoc chia se giua hai chuoi.

Mot trong nhung thach thuc ky thuat quan trong cua fork la thuc hien bao ve chong phat lai. Khi khong co bao ve chong phat lai, mot giao dich duoc phat tren mot chuoi co the duoc phat lai tren chuoi kia, co the khien nguoi dung vo tinh chi tieu tien tren ca hai chuoi. Bitcoin Cash da thuc hien bao ve chong phat lai manh me bang cach sua doi thuat toan ky giao dich. Cu the, Bitcoin Cash gioi thieu mot co SigHash moi (SIGHASH_FORKID) duoc bao gom trong hash cua moi chu ky giao dich. Cac giao dich duoc ky voi co nay la hop le tren chuoi Bitcoin Cash nhung khong hop le tren chuoi Bitcoin, va nguoc lai. Dieu nay dam bao su tach biet ro rang giua hai mang luoi tu thoi diem fork.

Gioi han kich thuoc block ban dau cho Bitcoin Cash duoc dat o muc 8MB, gap tam lan gioi han 1MB cua Bitcoin. Dieu nay dai dien cho su tang dang ke ve dung luong giao dich on-chain, cho phep Bitcoin Cash xu ly nhieu giao dich hon dang ke trong moi block trong khi duy tri phi thap. Block Bitcoin Cash dau tien sau fork duoc dao boi pool dao ViaBTC va co kich thuoc khoang 1,9MB, cho thay loi ich thuc te ngay lap tuc cua kich thuoc block lon hon.

Fork cung loai bo SegWit, von da duoc kich hoat tren chuoi Bitcoin. Cac nha phat trien Bitcoin Cash tu choi SegWit vi nhieu ly do: ho tin rang no mang lai su phuc tap khong can thiet cho giao thuc, tao ra mot he thong giao dich hai tang voi cac cau truc phi khac nhau, va sua doi cau truc block theo cach ma ho cho la lam suy yeu tinh don gian cua mo hinh UTXO. Bang cach chon tang kich thuoc block truc tiep thay vi do, Bitcoin Cash duy tri mot kien truc giao thuc don gian hon va truyen thong hon giong Bitcoin.

Sau fork, ca hai chuoi deu phai doi mat voi thach thuc dieu chinh do kho. Bitcoin Cash ban dau su dung cung do kho SHA-256 tu chuoi Bitcoin, nhung voi hash power danh cho dao it hon dang ke. De ngan chan tinh huong cac block duoc dao cuc ky cham, Bitcoin Cash da thuc hien co che Dieu chinh Do kho Khan cap (EDA) se giam do kho 20 phan tram neu it hon 6 block duoc dao trong khoang thoi gian 12 gio. Trong khi co che nay thanh cong trong viec giu cho chuoi hoat dong trong giai doan ban dau quan trong, no da cho thay khong on dinh, gay ra nhung bien dong manh liet trong thoi gian san xuat block va hash rate khi cac tho dao chuyen doi giua Bitcoin va Bitcoin Cash dua tren loi nhuan. EDA duoc thay the vao thang 11 nam 2017 bang mot thuat toan dieu chinh do kho on dinh hon dua tren trung binh dong cua 144 block truoc do.

Fork da gap phai tranh cai dang ke trong cong dong tien dien tu rong lon hon. Nhung nguoi chi trich cho rang Bitcoin Cash la mot no luc bat hop phap de chiem doat thuong hieu Bitcoin, trong khi nhung nguoi ung ho khang dinh rang do la su tiep noi hop phap cua lo trinh ban dau cua Bitcoin. Cac san giao dich va nha cung cap dich vu phai dua ra quyet dinh nhanh chong ve viec co ho tro chuoi moi hay khong va xu ly viec phan phoi coin da fork cho khach hang cua ho nhu the nao. Bat chap tranh cai, Bitcoin Cash nhanh chong khang dinh minh la mot loai tien dien tu kha thi va duoc su dung tich cuc, dat duoc khoi luong giao dich dang ke va viec chap nhan cua thuong nhan trong nhung thang sau fork.

Technical Specifications

Bitcoin Cash chia se kien truc ky thuat co ban cua Bitcoin, bao gom co che dong thuan proof-of-work SHA-256, mo hinh giao dich UTXO, duong cong elliptic secp256k1 cho chu ky so, va khoang thoi gian block muc tieu muoi phut. Tuy nhien, mot so sua doi chinh phan biet no voi giao thuc Bitcoin.

Su khac biet noi bat nhat la gioi han kich thuoc block. Bitcoin Cash ra mat voi gioi han kich thuoc block 8MB va sau do tang len 32MB vao thang 5 nam 2018. Gioi han 32MB nay cung cap dung luong giao dich gap khoang 32 lan so voi kich thuoc block hieu qua 1MB khong co SegWit cua Bitcoin (hoac gap khoang 8 lan dung luong cua gioi han hieu qua duoc tang cuong boi SegWit cua Bitcoin khoang 4MB). Kich thuoc block lon hon la nen tang cua triet ly mo rong on-chain cua Bitcoin Cash, cung cap khong gian rong rai cho su tang truong giao dich ma khong co ap luc phi phat sinh khi cac block lien tuc day.

Bitcoin Cash khong trien khai Segregated Witness (SegWit). Thay vi tach du lieu chung nhan khoi du lieu giao dich nhu SegWit, Bitcoin Cash giu nguyen dinh dang giao dich Bitcoin goc. Tat ca du lieu giao dich, bao gom chu ky, duoc luu tru trong block theo cach truyen thong. Dieu nay don gian hoa giao thuc va duy tri kha nang tuong thich nguoc voi phan mem va co so ha tang Bitcoin cu.

Mot cai tien giao thuc quan trong trong Bitcoin Cash la thuat toan SigHash duoc cai thien, duoc gioi thieu vao thoi diem fork. Thuat toan moi, dua tren BIP 143 (ban dau duoc phat trien cho SegWit), khac phuc van de bam bac hai ton tai trong so do xac minh chu ky Bitcoin goc. Trong so do goc, chi phi tinh toan de xac minh chu ky cua mot giao dich tang theo bac hai voi so luong dau vao, tao ra mot vector tan cong tu choi dich vu tiem nang. Thuat toan SigHash moi lam cho chi phi xac minh tro thanh tuyen tinh, cho phep mang luoi xu ly cac giao dich lon hon va phuc tap hon mot cach an toan.

Bitcoin Cash ho tro kich thuoc giao dich toi da lon hon va so luong thao tac chu ky (sigops) lon hon moi block so voi Bitcoin. Gioi han sigops duoc mo rong ty le voi kich thuoc block, dam bao chi phi tinh toan cua viec xac thuc block van duoc gioi han trong khi cho phep nhieu giao dich hon dang ke moi block.

He thong scripting trong Bitcoin Cash da duoc phat trien tich cuc vuot ra ngoai cach tiep can tuong doi bao thu cua Bitcoin. Bitcoin Cash da kich hoat lai va gioi thieu nhieu opcode mo rong kha nang bieu dat cua ngon ngu scripting. Cac bo sung dang chu y bao gom OP_CHECKDATASIG va OP_CHECKDATASIGVERIFY, cho phep cac script giao dich xac minh chu ky doi voi du lieu tuy y (khong chi du lieu giao dich), cho phep cac hop dong thong minh dua tren oracle va cac mau scripting nang cao khac. Opcode OP_REVERSEBYTES, cac opcode introspection ban dia, va gioi han script va stack lon hon da tang cuong them kha nang lap trinh cua Bitcoin Cash.

Bitcoin Cash su dung cung nen tang dinh dang dia chi nhu Bitcoin nhung da ap dung dinh dang CashAddr vao thang 1 nam 2018 de ngan chan su nham lan va loi gui giua cac chuoi. Dia chi CashAddr bat dau voi tien to "bitcoincash:" (thuong duoc viet tat thanh "q" hoac "p" cho phan hash) va su dung mot so do ma hoa khac voi dinh dang base58check cua Bitcoin. Su phan biet truc quan nay lam ro ngay lap tuc mot dia chi thuoc ve Bitcoin hay Bitcoin Cash, giam rui ro nguoi dung vo tinh gui tien den chuoi sai.

Mang luoi hoat dong tren cong 8333, cung cong mac dinh nhu Bitcoin, mac du cac node Bitcoin Cash tu nhan dang bang mot so magic mang khac trong qua trinh bat tay giao thuc. Dieu nay co nghia la cac node Bitcoin va Bitcoin Cash se khong vo tinh ket noi voi nhau mac du su dung cung mot cong.

Transaction Throughput and Scalability

Thong luong giao dich va kha nang mo rong la trung tam trong de xuat gia tri cua Bitcoin Cash. Luan diem co ban cua du an la: tien mat dien tu ngang hang phai xu ly giao dich nhanh va re de co the su dung hang ngay, va mo rong on-chain bang cach tang kich thuoc block la cach dang tin cay nhat de dat duoc dieu do.

Voi gioi han kich thuoc block 32MB va khoang thoi gian block muoi phut, Bitcoin Cash co thong luong toi da ve mat ly thuyet khoang 100 giao dich moi giay, tuy thuoc vao kich thuoc giao dich trung binh. Day la buoc nhay lon so voi gioi han ly thuyet cua Bitcoin khoang 7 giao dich moi giay voi block 1MB. Tren thuc te, thong luong phu thuoc vao loai giao dich va kich thuoc du lieu, nhung dung luong cua Bitcoin Cash hien tai van du suc cho khoi luong giao dich hien co, voi cac block thuong nho hon nhieu so voi gioi han 32MB.

Luong khong gian block du thua co tac dong truc tiep va do luong duoc den phi giao dich. Khi block khong day, khong co canh tranh phi, va giao dich co the duoc xac nhan voi phi rat thap. Muc phi relay toi thieu mac dinh cua Bitcoin Cash la 1 satoshi moi byte (1 satoshi = 0.00000001 BCH), va phan lon giao dich duoc xac nhan trong block ke tiep o muc gan toi thieu nay. Dieu nay lam cho phi giao dich tren Bitcoin Cash thuong chi la mot phan cua cent trong dieu kien binh thuong, trong khi phi tren Bitcoin co the dao dong tu vai do la den hang chuc do la trong thoi ky tac nghen.

Cong dong phat trien Bitcoin Cash da thuc hien nhieu nghien cuu va thu nghiem ve gioi han cua mo rong on-chain. Sang kien Gigablock Testnet (2017-2018) cho thay giao thuc Bitcoin co the xu ly cac block 1GB hoac hon neu co toi uu phan mem phu hop va phan cung hien dai. Cac bai test nay chi ra nhieu nut that trong codebase goc, bao gom truyen block, xac thuc giao dich va quan ly tap UTXO, va dinh huong cho cac no luc toi uu tiep theo.

Nhieu cai tien cap giao thuc va trien khai da duoc thuc hien de ho tro block lon. Graphene, mot giao thuc truyen block dua tren invertible Bloom lookup tables va Bloom filters, giam manh bang thong can thiet bang cach ma hoa chi phan khac biet giua block va cac giao dich ma node nhan da co trong mempool. Canonical Transaction Ordering (CTOR), kich hoat thang 11 nam 2018, yeu cau cac giao dich trong block duoc sap xep theo transaction ID. Thay doi tuong nhu nho nay cho phep toi uu dang ke trong xac thuc va truyen block, vi no ho tro xac thuc song song va cac thuat toan doi chieu tap hieu qua hon.

Cac sang kien UTXO commitment va parallel validation tiep tuc cai thien kha nang xu ly block lon mot cach hieu qua. Bang cach tan dung CPU da nhan va luu tru SSD, cac trien khai node toi uu co the xac thuc cac block chua hang chuc nghin giao dich trong thoi gian chap nhan duoc.

Lo trinh mo rong cua Bitcoin Cash huong toi viec tiep tuc tang gioi han kich thuoc block khi cong nghe va nhu cau can thiet. Cac nha phat trien nhan manh muc tieu dai han la ho tro luong thanh toan quy mo toan cau hoan toan on-chain, nham den thong luong du de phuc vu hang ty giao dich moi ngay. Day la muc tieu tham vong, nhung su tien bo lien tuc ve phan cung, bang thong va toi uu phan mem tao ra con duong kha tin de dat duoc no theo cach tang dan theo thoi gian.

Mot khia canh quan trong trong cach tiep can mo rong cua Bitcoin Cash la "giao dich zero-confirmation". Doi voi thanh toan gia tri thap, cua hang co the chap nhan giao dich ngay khi no duoc phat tan, truoc khi duoc dua vao block. Bitcoin Cash da trien khai mot so bien phap de tang do tin cay cho zero-conf, bao gom quy tac "first-seen" (node chi relay phien ban dau tien cua giao dich ma no thay, lam kho cac co gang double-spend) va cac giao thuc thong bao double-spend de canh bao cua hang khi phat hien giao dich xung dot. Nhung bien phap nay giup Bitcoin Cash phu hop voi thanh toan tai diem ban hang, noi viec cho doi muoi phut cho xac nhan block la khong thuc te.

OP_RETURN and Data Applications

Bitcoin Cash ho tro opcode OP_RETURN, cho phep nguoi dung chen du lieu tuy y len blockchain thong qua mot output giao dich duoc thiet ke de khong the chi tieu. Tinh nang nay mo ra nhieu ung dung tap trung vao du lieu xay dung tren blockchain Bitcoin Cash, bao gom cac giao thuc token, he thong nhan tin, dich vu cong chung thuc (notarization), va cac nen tang mang xa hoi.

Gioi han du lieu OP_RETURN tren Bitcoin Cash duoc dat o muc 220 byte moi output, lon hon dang ke so voi gioi han 80 byte cua Bitcoin. Ngoai ra, Bitcoin Cash cho phep nhieu output OP_RETURN trong mot giao dich, tiep tuc mo rong luong du lieu co the chen trong mot lan ghi. Cac gioi han "rong" nay, ket hop voi phi giao dich thap, lam cho Bitcoin Cash tro thanh nen tang kinh te hop ly cho cac ung dung du lieu ma tren cac chain bi han che dung luong se rat dat do.

Simple Ledger Protocol (SLP) la mot trong nhung he thong token som va pho bien nhat tren Bitcoin Cash su dung OP_RETURN. SLP cho phep tao va chuyen token tuy bien tren blockchain Bitcoin Cash bang cach ma hoa metadata token trong output OP_RETURN. Ve sau, SLP phan lon da duoc thay the boi CashTokens, nhung no da chung minh tinh kha thi cua viec xay dung nen kinh te token tren mo hinh UTXO.

CashTokens, kich hoat vao thang 5 nam 2023, dai dien cho cach tiep can token hoa tinh vi hon tren Bitcoin Cash. Khac voi SLP (dua vao metadata OP_RETURN co the bi bo qua boi giao thuc co so), CashTokens la mot tinh nang cap consensus tich hop token truc tiep vao mo hinh UTXO. Moi UTXO co the mang ca gia tri BCH va token di kem, va tinh hop le cua token duoc dam bao boi cac quy tac consensus. CashTokens ho tro hai loai token: token fungible (tuong tu ERC-20 tren Ethereum) va token khong the thay the (NFT). Vi token duoc thuc thi o cap consensus, giao dich token co cung muc bao mat nhu giao dich BCH goc, giam nhu cau tin cay va giam phu thuoc vao cac he thong index cua cac giao thuc overlay nhu SLP.

Memo.cash la mot giao thuc mang xa hoi phi tap trung xay dung tren Bitcoin Cash bang cac giao dich OP_RETURN. Nguoi dung phat cac bai viet, theo doi, thich va cac hanh dong xa hoi khac duoi dang giao dich Bitcoin Cash co du lieu OP_RETURN da ma hoa. Vi du lieu duoc luu tren blockchain, no co tinh chong kiem duyet va duoc luu tru lau dai. Chi phi giao dich thap tren Bitcoin Cash lam cho cach lam nay co the chap nhan ve kinh te: moi hanh dong xa hoi chi ton mot phan nho cua cent.

Cac ung dung du lieu khac bao gom dong dau thoi gian tai lieu va dich vu cong chung thuc, noi hash cua tai lieu duoc chen vao OP_RETURN de tao bang chung bat bien ve su ton tai cua tai lieu tai mot thoi diem cu the. Theo doi chuoi cung ung, xac thuc chung chi, va he thong dinh danh phi tap trung cung da duoc xay dung dua tren kha nang nhung du lieu cua Bitcoin Cash.

Su ket hop giua dung luong OP_RETURN lon, phi thap va thoi gian xac nhan nhanh giup Bitcoin Cash tro thanh mot lua chon canh tranh cho cac ung dung du lieu tren blockchain. Du cac blockchain chuyen dung cho du lieu ton tai, Bitcoin Cash co loi the la mang luoi da duoc thiet lap, bao mat cao, duoc ho tro rong rai va co thanh tich van hanh lien tuc da duoc chung minh.

Network Architecture

Mang Bitcoin Cash hoat dong tren kien truc peer-to-peer co ban giong Bitcoin, voi cac node giao tiep qua giao thuc gossip de phat tan giao dich va block. Cac node day du duy tri mot ban sao day du cua blockchain va tu minh xac thuc tat ca giao dich va block theo cac quy tac consensus. Mang la khong can cap phep (permissionless), nghia la bat ky ai cung co the chay node va tham gia ma khong can xin phep.

Co nhieu trien khai node day du doc lap cho Bitcoin Cash, phan anh cam ket cua du an doi voi phat trien phi tap trung. Bitcoin Cash Node (BCHN) la trien khai duoc su dung pho bien nhat va dong vai tro client tham chieu thuc te. Cac trien khai khac bao gom Bitcoin Unlimited, BCHD (viet bang Go), va Knuth (một trien khai C++ hieu nang cao). Su ton tai cua nhieu trien khai doc lap giam rui ro mot loi phan mem duy nhat gay su co tren toan mang, va giup dam bao khong co mot nhom phat trien nao co quyen kiem soat don phuong doi voi giao thuc.

Khai thac tren Bitcoin Cash su dung thuat toan proof-of-work SHA-256 giong Bitcoin. Dieu nay co nghia la cung mot phan cung ASIC co the dung de dao Bitcoin hoac Bitcoin Cash, va tho dao co the chuyen doi giua hai chain dua tren loi nhuan. Tren thuc te, hash rate cua Bitcoin Cash chi la mot phan nho so voi Bitcoin, vi phan lon suc manh SHA-256 duoc huong den chain Bitcoin co loi nhuan cao hon. Tuy nhien, thuat toan dieu chinh do kho cua Bitcoin Cash dam bao cac block van duoc san xuat theo muc tieu muoi phut bat ke muc hash rate tuyet doi.

Thuat toan dieu chinh do kho la mot trong nhung thanh phan quan trong nhat cua Bitcoin Cash. Co che dieu chinh goc cua Bitcoin (tinh lai moi 2016 block, khoang hai tuan) qua cham de thich ung voi bien dong hash rate nhanh khi tho dao lien tuc chuyen qua lai giua Bitcoin va Bitcoin Cash. Sau giai doan Emergency Difficulty Adjustment (EDA) gay nhieu van de nam 2017, Bitcoin Cash da ap dung thuat toan moi vao thang 11 nam 2017, dieu chinh do kho dua tren cua so truot 144 block.

Vao thang 11 nam 2020, Bitcoin Cash nang cap len thuat toan dieu chinh do kho ASERT (Absolutely Scheduled Exponentially Rising Targets), con goi la aserti3-2d. ASERT dieu chinh muc tieu do kho dua tren chenhlech giua thoi gian thuc te da troi qua va thoi gian ky vong tinh tu mot block tham chieu ("anchor block"). Neu block duoc tao nhanh hon du kien, do kho tang theo ham mu; neu cham hon, do kho giam theo ham mu. Ky hieu "3-2d" chi nua doi khoang hai ngay (cu the 288 block o muc tieu muoi phut), nghia la neu hash rate tang gap doi hoac giam mot nua lien tuc, do kho se dieu chinh day du trong khoang hai ngay. ASERT da chung to rat on dinh, giup giu khoang cach block nhat quan ke ca khi hash rate bien dong manh.

Hieu qua truyen block la rat quan trong doi voi mang co block lon. Bitcoin Cash da ap dung nhieu toi uu de dam bao block lon co the lan truyen nhanh. Compact Blocks (BIP 152) cho phep node tai tao block tu transaction ID thay vi tai toan bo du lieu giao dich, giam manh bang thong can thiet khi cac node co mempool giong nhau. Graphene cung cap muc nen cao hon bang cach dung cac cau truc du lieu xac suat de ma hoa block gan toi uu. Xthinner la mot giao thuc nen khac duoc phat trien rieng cho Bitcoin Cash, co the dat ty le nen rat cao doi voi cac block thong thuong.

Chinh sach relay va mempool cua mang duoc thiet ke de ho tro giao dich zero-confirmation dang tin cay. Cac node ap dung quy tac first-seen nghiem ngat, chi chap nhan va relay phien ban dau tien cua giao dich ma no quan sat duoc. Neu phat hien giao dich thu hai co gang chi tieu cung dau vao (double-spend), node se tao bang chung double-spend va phat tan de canh bao cua hang va cac ben lien quan. Ha tang nay cung cap muc bao ve hop ly khi chap nhan giao dich chua duoc xac nhan cho cac thanh toan gia tri thap trong doi song.

Smart Contract Capabilities

Mac du Bitcoin Cash chu yeu duoc thiet ke nhu mot he thong tien mat dien tu ngang hang, no da phat trien kha nang smart contract dang ke thong qua cac mo rong cua ngon ngu script. Khac voi mo hinh smart contract Turing-complete theo kieu account-based cua Ethereum, smart contract tren Bitcoin Cash hoat dong trong mo hinh UTXO voi ngon ngu script dua tren stack va co y khong Turing-complete. Thiet ke nay giup chi phi thuc thi du doan duoc va tranh nhom lo hong lien quan den tinh toan khong gioi han, nhung van cho phep tao ra nhieu cong cu tai chinh lap trinh duoc mot cach bat ngo.

Ngon ngu script cua Bitcoin Cash duoc nang cap dan dan thong qua nhieu dot nang cap giao thuc. Vao thang 5 nam 2018, nhieu opcode tung bi vo hieu hoa tu som trong lich su Bitcoin da duoc bat lai, bao gom cac toan tu logic bitwise (OP_AND, OP_OR, OP_XOR), cac toan tu so hoc cho so lon, va cac thao tac xu ly chuoi (OP_SPLIT, OP_CAT). Nhung opcode nay mo rong dang ke do bieu dat cua script.

Viec gioi thieu OP_CHECKDATASIG va OP_CHECKDATASIGVERIFY vao thang 11 nam 2018 la mot buoc tien quan trong. Cac opcode nay cho phep script xac minh chu ky ECDSA tren du lieu tuy y, khong chi tren chinh giao dich. Dieu nay mo duong cho cac hop dong dua tren oracle, noi mot nguon du lieu ben ngoai ky mot thong diep xac nhan mot dieu kien thuc te (vi du gia, thoi tiet, ket qua the thao), va viec thuc thi hop dong phu thuoc vao noi dung thong diep do. Kha nang nay cho phep thi truong du doan phi tap trung, hop dong bao hiem, va cac cong cu tai chinh phu thuoc du lieu ben ngoai.

Cac opcode introspection ban dia, duoc gioi thieu vao thang 5 nam 2022, cho phep script xem thuoc tinh cua giao dich chua no. Script co the kiem tra gia tri, locking script va du lieu token cua ca input va output trong cung giao dich. Dieu nay cho phep cac hop dong kieu covenant: script han che cach dong tien co the duoc chi tieu trong tuong lai, khong chi han che ai duoc chi tieu. Covenants cho phep cac mau manh nhu vaults (han che chi tieu theo thoi gian de tang bao mat), thanh toan dinh ky, san giao dich phi tap trung, va bo phieu on-chain.

CashScript la ngon ngu smart contract cap cao cho Bitcoin Cash, tuong tu Solidity tren Ethereum. CashScript cho phep viet hop dong voi cu phap giong JavaScript va bien dich xuong bytecode script cua Bitcoin Cash. Ngon ngu nay giam bot do kho cua thiet ke hop dong UTXO (introspection input/output, xac minh chu ky), giup no de tiep can hon voi cac lap trinh vien khong quen voi lap trinh stack cap thap. CashScript da duoc dung de xay dung san giao dich phi tap trung, escrow, crowdfunding va cac ung dung khac.

Nang cap CashTokens vao thang 5 nam 2023 bo sung them mot lop kha nang cho smart contract. Bang cach tich hop token fungible va NFT truc tiep vao mo hinh UTXO o cap consensus, CashTokens cho phep cac hop dong dua tren token duoc thuc thi boi quy tac consensus thay vi giao thuc overlay. NFT trong CashTokens co truong "commitment": du lieu tuy y gan vao token ma script co the doc va xac thuc. Dieu nay tao co che giu trang thai on-chain qua nhieu giao dich, dieu tung kho trong mo hinh UTXO. Hop dong co the dung NFT lam vat mang trang thai, cap nhat commitment moi lan giao dich de thuc hien cac quy trinh nhieu buoc.

Su ket hop giua opcode introspection, CashTokens va CashScript tao nen mot nen tang smart contract co kha nang, du khac co ban voi mo hinh cua Ethereum, nhung van co the trien khai nhieu ung dung DeFi tuong tu. San giao dich phi tap trung, AMM, giao thuc cho vay, va DAO da duoc xay dung hoac thu nghiem tren Bitcoin Cash. Cach tiep can UTXO co loi the ve song song hoa (UTXO xac thuc doc lap), quyen rieng tu (moi UTXO tach biet) va tinh du doan (khong co trang thai toan cuc), nhung doi hoi cac mau thiet ke khac voi he thong account-based.

Monetary Policy

Bitcoin Cash ke thua toan bo chinh sach tien te cua Bitcoin. Tong cung Bitcoin Cash bi gioi han o 21 trieu coin, va lich phat hanh theo co che halving giong Bitcoin. Dieu nay la he qua truc tiep cua fork: vi Bitcoin Cash tach ra tu blockchain Bitcoin, no bat dau voi cung lich su phat hanh va tiep tuc ap dung cung quy tac phat hanh trong tuong lai.

Block reward bat dau tu 50 BCH moi block (ke thua tham so genesis cua Bitcoin) va giam mot nua moi 210,000 block, xap xi moi bon nam. Lan halving dau tien xay ra thang 11 nam 2012 (truoc fork, nen la lich su chung), giam reward con 25 coin. Lan halving thu hai thang 7 nam 2016 giam con 12.5 coin. Lan halving thu ba thang 4 nam 2020, sau fork nen chi ap dung cho chain Bitcoin Cash, giam con 6.25 BCH. Lan halving thu tu thang 4 nam 2024 tiep tuc giam con 3.125 BCH moi block.

Lich halving nay tao ra chinh sach tien te giam dan (disinflationary), noi toc do tao coin moi giam theo thoi gian va tien ve 0 theo kieu tiem can. Dong BCH cuoi cung du kien se duoc dao vao khoang nam 2140. Khi do, thu nhap cua tho dao se chi con den tu phi giao dich.

Tran 21 trieu va lich halving mang lai cho Bitcoin Cash tinh khan hiem giong Bitcoin. Tinh den dau nam 2026, luong BCH luu hanh uoc tinh khoang 19.8 trieu, tuong duong hon 94% tong cung se ton tai. So coin con lai se duoc phan phoi trong hon mot the ky, voi reward giam dan.

Cach Bitcoin Cash tiep can chuyen doi tu block subsidy sang phi giao dich co diem khac voi chien luoc cua Bitcoin. Trien ly mo rong cua Bitcoin han che khong gian block de duy tri thi truong phi, va ngam dinh can phi cao moi giao dich de bu dap cho tho dao khi reward giam. Bitcoin Cash chon huong nguoc lai: giu phi thap va block lon, nham tao du doanh thu phi tong cong thong qua khoi luong giao dich lon thay vi phi cao moi giao dich. Trong mo hinh nay, neu moi giao dich chi tra 1 cent nhung mang xu ly hang trieu giao dich moi block, tong doanh thu phi van co the du lon de khuyen khich khai thac.

Mo hinh dua tren khoi luong nay yeu cau Bitcoin Cash dat thong luong giao dich cao hon dang ke so voi Bitcoin de tao ra muc khuyen khich tuong duong trong giai doan hau subsidy. Nguoi ung ho lap luan rang dieu nay co the dat duoc nho mo rong on-chain lien tuc, vi nhu cau thanh toan toan cau la khong lo, va chi can chiem mot phan nho giao dich the gioi da la hang trieu thanh toan moi ngay. Nguoi chi trich cho rang muc do chap nhan nay khong chac chan va mo hinh phi thap co the khong du dong luc trong qua trinh chuyen doi.

Chinh sach tien te chung giua Bitcoin va Bitcoin Cash cung co nghia la hai chain canh tranh truc tiep ve SHA-256 hash power. Tho dao phan bo tai nguyen vao chain co loi nhuan cao hon tai moi thoi diem, va thuat toan dieu chinh do kho tren ca hai chain deu thich ung voi viec phan bo linh hoat nay. Tren thuc te, ty le hash rate cua Bitcoin Cash trong tong SHA-256 thuong tuong ung voi gia tuong doi cua no, phan anh hanh vi kinh te hop ly cua tho dao toi uu loi nhuan.

Conclusion

Bitcoin Cash dai dien cho su tiep noi co nguyen tac cua tam nhin Bitcoin ban dau: tien mat dien tu ngang hang. Bang cach tang gioi han kich thuoc block va theo duoi mo rong on-chain, Bitcoin Cash giu duoc phi thap va giao dich nhanh giong thoi ky dau cua Bitcoin, giup no phu hop voi thanh toan hang ngay va microtransactions ma whitepaper goc huong den.

Lo trinh ky thuat cua du an duoc danh dau boi nhung cai tien giao thuc co y nghia. Thuat toan dieu chinh do kho ASERT giup tao block on dinh duoi bien dong hash rate. He thong script duoc mo rong voi opcode duoc khoi phuc va opcode moi, cho phep smart contract phuc tap trong gioi han an toan cua mo hinh UTXO. CashTokens mang token hoa duoc thuc thi boi consensus vao giao thuc theo phong cach Bitcoin lan dau tien. CashScript lam cho nhung kha nang nay de tiep can hon voi cong dong lap trinh vien. Tong hop lai, cac buoc tien nay cho thay mo hinh UTXO co the ho tro he sinh thai ung dung phi tap trung phong phu ma van giu duoc su don gian va bao mat co ban.

Cuoc tranh luan ve mo rong dan den su ra doi cua Bitcoin Cash nhan manh mot cang thang co ban trong he thong phi tap trung: danh doi giua dung luong on-chain va chi phi van hanh node day du. Bitcoin Cash chon uu tien dung luong giao dich va trai nghiem nguoi dung, lap luan rang loi ich kinh te cua viec duoc su dung rong rai vuot qua yeu cau phan cung cao hon doi voi nguoi van hanh node. Day la cau hoi thuc nghiem, se duoc tra loi trong nhieu nam va thap ky toi khi ca Bitcoin va Bitcoin Cash tiep tuc tien hoa theo con duong rieng.

Su ton tai va phat trien lien tuc cua Bitcoin Cash qua nhieu chu ky giam gia, qua cac fork gay tranh cai (noi bat la vu tach Bitcoin SV thang 11 nam 2018) va qua no luc cong dong ben bi cho thay tinh ben vung cua du an va niem tin cua nhung nguoi tham gia. Mang da xu ly hang tram trieu giao dich ke tu khi fork, duy tri van hanh lien tuc, va thu hut cong dong toan cau gom lap trinh vien, thuong nhan va nguoi dung tin rang tien mat dien tu ngang hang la cong nghe dang de xay dung.

Thanh cong dai han cua Bitcoin Cash phu thuoc vao kha nang thu hut nguoi dung va thuong nhan coi trong giao dich on dinh, phi thap, va phu thuoc vao viec mo rong ha tang de dap ung nhu cau cua mang thanh toan toan cau. Nen tang ky thuat la vung chac, lo trinh ro rang, va cong dong cam ket. Viec Bitcoin Cash co dat duoc muc tieu tham vong tro thanh tien mat dien tu cho the gioi hay khong se khong chi do boi gioi han ky thuat, ma boi hieu ung mang luoi, dong luc thi truong va mau hinh chap nhan chi phoi su tien hoa cua moi he thong tien te.