To run bitcoin core testnet on Ubuntu 16.04

How can I run Bitcoin core testnet version on ubuntu 16.04 platform ? I am getting so many reference about how to run bitcoin core mainnet but it will take around 20 days to synchronize with the network as per my bandwidth and also will take my half of the HDD. So I opt for Testnet. Can someone explain me how to insatll bitcoin core testnet on Ubuntu 16.04? I would be grateful. Step by step explanation or reference would be much appreciated.

Encrypted message with nLockTime

I know you can delay a transaction’s accepted date by using nLockTime. I’m still looking for the simplest way to generate a transaction with nLockTime, but that’s another topic.

I’m wondering if there’s a way to use this feature to send a message that will only decrypt after the time is due.

I know that a transaction broadcast with nLockTime already has all details visible and the amount is simply not yet spendable by the recipient. Is there a way to also make the note on that transaction encrypted until such date? Can I use bitmessage to achieve this somehow? How about another coin such as Dash or zCash which I assume also encrypt the transaction’s note to anyone except the recipient [do they actually do this, especially Dash]?

The idea is to send a message that only the recipient can decrypt and only after a certain date, with no manual intervention in the future, nor anything else involved. It would be ideal if they received that message in their wallet like any transaction after it’s due, but the message shouldn’t be viewable by others nor by the recipient in advance searching, say, in a block explorer.

Thank you

Bitpay Without Credit Card

I am having trouble finding this information so I would like to ask those who use BitPay:

  1. Can you create a BitPay account and spend coins without having a Credit/Debit Card associated with your account?
  2. Tying into the first question can you use Bitpay without tying any personal information to your Bitpay account?

Some stores only accept bitcoin via Bitpay but I don’t want to create a Bitpay account if it removes my anonymity.

IOUs – Cold wallet relationship (Poloniex, Kraken, Gatehub)

(I’m new to cryptocurrencies.)

Please answer the following questions seperately for Poloniex and Kraken if they behave differently.

1) Can I buy example given XRP on Poloniex or Kraken and send it from there to my cold wallet?

2) Are these XRP on Poloniex or Kraten IOUs?

3) If they are IOUs and I send the XRPs to my cold wallet, does it effect my money on my cold wallet if Poloniex or Kraken goes broke (do I loose my money in that scenario)?

4) Is there any difference between sending my XRPs from Kraken/Poloniex to my coldwallet and sending my XRPs from Gatehub to my coldwallet?

Applying additional oauth scopes to coinbase

I am trying to apply the coinbase wallet API with oauth to use its send functionality. I have been able to connect to the API and use its endpoints, but whenever I try to use the send functionality, I am thrown the error Invalid amount for meta[send_limit_amount]. My omniauth initializer looks like this:

provider :coinbase, , ENV['CLIENT_ID'], ENV['CLIENT_SECRET'], 
scope: 'wallet:user:read wallet:user:email wallet:accounts:read wallet:transactions:send'

The reason for this error is because, in order to use the send functionality, coinbase requires additional parameter meta[send_limit_amount]. Where and how am I supposed to apply this additional scope?