CBSA Sample Questions Answers

Blockchain 1.0, Grandpa Bitcoin

Smart contracts generally are not legal contracts. However, its possible that a smart contract could be accepted as a legal contract but not normally. Read more about Smart contracts here

The gas price is a value set by the creator of the transaction, who has to pay gas_price * gas up front from the sending account. If some gas is left after the execution, it is refunded in the same way. If the gas is used up at any point (i.e. it is negative), an out-of-gas exception is triggered, which reverts all modifications made to the state in the current call frame.

SHA-2 consists of a set of 6 hashing algorithms, and is considered the strongest. SHA-256 or above is recommended for situations are security is vital. SHA-256 produces 32-byte hash values.

Sometimes referred to as “private” blockchains, you are required to have some sort of permission to access any or parts of that blockchain. There are a multitude of variants and hybrid permissioned/permissionless blockchains that exist.

XOR or “Exclusive OR” is a logic gate.

A chaincode package that was signed at creation can be handed over to other owners for inspection and signing. The workflow supports out-of-band signing of chaincode package.

Review Technical Whitepaper https://www.corda.net/ Corda network has one or more notary services which provide transaction ordering and timestamping services, thus abstracting the role miners play in other systems into a pluggable component.

Difficulty and Timestamp block also contains two very important parameters: a difficulty and a timestamp. The difficulty regulates how hard it is to find a block by the miner. The mining time is set to be between 10 and 20 seconds. If it’s beyond 20 seconds, the difficulty is too high and will be automatically lowered going forward. If the mining happens below 10 seconds, then the difficulty increases. The timestamp is the time when a miner found the block. It is not automatically derived, rather it is set by the miner itself and can thus be influenced to a certain degree. The timestamp does not depend on the time zone, as it’s the standard Unix timestamp.

If you send off a transaction, then several fields have to be set. These include: • nonce: It is a sequence number for the sending account which counteracts replay attacks • gasprice: price offered to pay per gas • startgas: upper limit for the gas consumption • to: destination address (EoA or contract address) • value: Ether to transfer • data: Data to transfer • v, r, s: ECDA signature.

The EVM is basically a sandboxed virtual machine running on every single node. It is Turing complete and a transaction-based state machine. The nodes reach consensus by executing all transactions. Only the miner node gets the block reward, all other nodes are just checking if the miner was “honest”.

The main disadvantages are huge expenditures, “uselessness” of computations and 51 percent attack.

The root of the tree is the topmost node and hence this tree is represented upside down. The bottommost nodes are called as leaf nodes. Each node is simply a cryptographic hash of a transaction. In the above diagram, Transaction A,B,C,C form the leaves of the tree.

Sidechain is another name for blockchains that run adjacent to Bitcoin and offer more scope for processing contracts.

Secure Registry Services enables Secured Docker Registry of base Hyperledger images and custom images containing chaincodes.