Process of Generating ProofCode

Step 1: Generate a Storage Proof Seed (ProofSeed)

ProofSeed = HexEncode(SHA256(originValue))

• originValue: When the appid is used for authentication, the value is obtained from the X-User-Id header in the request. In other authentication schemes, the value is obtained from the Authorization header in the request.
• SHA256(String): For a message of any length, SHA256 generates a 256-bit hash value, which is called a message digest.
• HexEncode(ByteArray): Base16 encoding function for returning a digest consisting of lowercase letters. Each byte you enter is expressed as two hexadecimal characters.

Step 2: Determine the Binary File Fragment Involved in the Storage Proof Calculation

Calculate the start and end positions of the binary file involved in the calculation.

Start = LongValueUnsigned(ByteSub(SHA256(ProofSeed),24,32))%size;
End = Start+8>=Size?Size:Start+8;

• SHA256(String): For a message of any length, SHA256 generates a 256-bit hash value, which is called a message digest.
• ByteSub(ByteArray,Integer,Integer): bytes in the specified range are extracted from the digest value. In this scenario, SHA256 returns 32 bytes. The last 8 bytes of the digest value are used, that is, the bytes in the range [24, 32).
• LongValueUnsigned (BitSet): the byte array is converted into an 8-byte integer. When implementing this function, the sign bit of the first byte must be removed to ensure that a positive integer is returned.
• size: size of the file (unit: byte).
• The binary file fragment involved in the storage proof calculation is the binary file fragment corresponding to the [Start, End) range.

Step 3: Calculate the Storage Proof

Obtain the corresponding array from the corresponding position of the binary file based on the binary fragment.

Data = readFile(file, start, end);
proofCode = HexEncode(SHA256(Data))

• readFile(File,Integer,Integer): the byte array is read from the specified range of the file.
• SHA256(ByteArray): For a message of any length, SHA256 generates a 256-bit hash value, which is called a message digest.
• HexEncode(ByteArray): Base16 encoding function for returning a digest consisting of lowercase letters. Each byte you enter is expressed as two hexadecimal characters.