Cypherium Virtual Machine Specification

The Cypherium Virtual Machine (CVM) is a register-based virtual machine inspired by the Dalvik (now part of the Android Runtime) architecture. The virtual machine from Ethereum VM and NEO VM also influenced its design. It is used for executing smart contracts on the Cypherium blockchain platform. A reference implementation is provided using the Go language.

Design Principle

CVM favors small and simple smart contracts that preferably only use the 65536 available registers (registers can be considered as directly addressable memory) without allocating extra memory. We envision a blockchain where there is a rich set of simple smart contracts that follow the UNIX philosophy "do one thing and do it well" at contract developers' disposal. Those contracts would together form a common library so that future contract developers will just call them for frequently-used functionalities. This, we reckon, promotes the code reusability which in turn prevents the blockchain size from bloating by eliminating code redundency.

The smart contracts that comprise the common library would preferably be developed and added into the blockchain from the team itself and the contract developing community, since they are guarenteed to provide high-quality code. Nevertheless, once on the blockchain, those contracts and their codes will be under public scrutiny.

Description

• Each contract is allocated with a contract frame with fixed size upon creation. Each contract frame consists of a particular number of registers (16-bit indexing namely, up to 65536) as well as any adjunct data needed to execute the contract.
• Each contract can access and manipulate data from 5 locations:
  1. Registers from its own contract frame (r/w)
  2. Persistent contract storage (r/w)
  3. On-chain data (ro)
  4. Message from the transaction that triggered the contract (ro)
  5. An optional infinitely expending memory (r/w)
• All memory region but the persistent contract storage will be cleared and deallocated upon exit.
• Gas mechanism similar to that of the EVM
• Use a PC counter to keep track of the next instruction
• Iteration counter (counts conditional jumps to prevent dead loops)

Instruction Format

• Dest-Source ordering format
• 8-bit opcode
• 16-bit register index
• Registers are able to hold arbitrary-precision data

Call Convention

Upon calling the CALL op, the runtime system checks the content of the register 65535 for the size N of the message, the actual content is constructed using the register (65535-1)-N to 65535-1. The message will be the input message to the callee.

Upon calling the the RET op for returning, the runtime will copy the content of N last consecutive registers(65535-1-N to 65535-1) from the callee's contract frame, specified by the register 65535 from the same contract frame, to the caller's last N registers.

Instruction Sets

• 256 (0x100) opcodes,
• %A, %B, etc. stands for arbitrary registers
• $INS stands for an instant value

Flow control (0x000 - 0x010)

• NOP : Do nothing
  • NOP
• ABORT : Abort the current execution and reverse all the changes
  • ABORT
• JMP : PC = %A/$INS
  • JMP %A
• JMPIF : if %B: PC = %A
  • JMPIF %A %B
• JMPIFNOT : if !%B: PC = %A
  • JMPIFNOT %A %B
• CALL : Call another contract with the contract address in %A
  • CALL %A
• RET: Return control to the caller
  • RET
• CREATE : Create a smart contract
  • CREATE

Environment (0x011 - 0x030)

• ADDRESS : Get address of currently executing account to %A
  • ADDRESS %A
• BALANCE : Get balance of the given account to %A
  • BALANCE %A
• ORIGIN : Get the sender's address to %A
  • ORIGIN %A
• CALLER : Get the callers address to %A
  • CALLER %A
• CALLVALUE : Get deposited value
  • CALLVALUE %A
• MSGSIZE :
  • MSGSIZE %A
• GASPRICE : Get gasprice
  • GASPRICE %A
• GAS : Get avaiable gas
  • GAS %A
• BLOCKHASH : Get the hash of one of the complete micro blocks (%A contains the index of the blocks and %A also will contain the result)
  • BLOCKHASH %A
• COINBASE : Get one of the micro block %B's beneficiary address (%A contains the index of the blocks and %A also will contain the result)
  • COINBASE %A
• TIMESTAMP : Get one of the key block's timestamp (%A contains the index of the blocks and %A also will contain the result)
  • TIMESTAMP %A
• DIFFICULTY : Get one of the key blocks' difficulty (%A contains the index of the blocks and %A also will contain the result)
  • DIFFICULTY %A

Bitwise logic (0x031 - 0x040)

• AND : %A = %A & %B
  • AND %A %B
• OR : %A = %A | %B
  • OR %A %B
• XOR : %A = %A XOR %B
  • XOR %A %B
• NOT : %A = ~%A
  • NOT %A
• BYTE : Retrieve byte %A[$INS] to %C
  • BYTE %C %A $INS

Load/Store (0x041 - 0x050)

• MOV : Load value %B/$INS to %A
  • MOV %A %B
  • MOVI %A $INS
• LDMSG : Load $INS-byte from message starting from index %B to %A
  • LDMSG %A %B $INS
• LDMEM : Load $INS-byte from memory starting from index %B to %A
  • LDMEM %A %B $INS
• LDSTG : Load $INS-byte from storage starting from index %B to %A
  • LDSTG %A %B $INS
• STMEM : Store %B to memory starting from index %A
  • STMEM %A %B
• STSTG : Store %B to storage starting from index %A
  • STSTG %A %B

Arithmetic (0x051 - 0x090)

In this section, the instant values ($INS) are interpreted as 64-bit signed integers

• INC : %A += 1
  • INC %A
• DEC : %A -= 1
  • DEC %A
• NEG : %A = -%A
  • NEG %A
• ABS : %B = |%A|
  • ABS %B %A
• ADD
  • ADD %C %A %B
  • ADDI %C %A $INS
• SUB
  • SUB %C %A %B
  • SUBI %C %A $INS
• MUL
  • MUL %C %A %B
  • MULI %C %A $INS
• DIV
  • DIV %C %A %B
  • DIVI %C %A $INS
• MOD
  • MOD %C %A %B
  • MODI %C %A $INS
• EXP : %C = %A ^ %B/$INS
  • EXP %C %A %B
  • EXPI %C %A $INS
• EQ : %C = %A == %B/$INS ? 1 : 0
  • EQ %C %A %B
  • EQI %C %A $INS
• LT : %C = %A < %B/$INS ? 1 : 0
  • LT %C %A %B
  • LTI %C %A $INS
• GT : %C = %A > %B/$INS ? 1 : 0
  • GT %C %A %B
  • GTI %C %A $INS
• LTE : %C = %A <= %B/$INS ? 1 : 0
  • LTE %C %A %B
  • LTEI %C %A $INS
• GTE : %C = %A >= %B/$INS ? 1 : 0
  • GTE %C %A %B
  • GTEI %C %A $INS
• MAX : %C = %A > %B/$INS ? %A : %B/$INS
  • MAX %C %A %B
  • MAXI %C %A $INS
• MIN : %C = %A < %B/$INS ? %A : %B/$INS
  • MIN %C %A %B
  • MINI %C %A $INS

Cryptography (0x091 - 0x100)

• SHA3 : %B = SHA3-256(%A)
  • SHA3 %B %A
• SHA3M : %B = MEM[%A:%A+$INS]
  • SHA3M %B %A $INS
• CHKSIG
• CHKMULSIG