Big Data, learning Pandas

I have enrolled in the MIT Big Data an Social Analytics certificate course because I enjoy learning new technologies, in particular technologies which can be applied in the area of fintech.

I find the Python programming language and the big data libraries interesting, and the learning curve at least so far is not so steep.


Below is a gist I’m putting together to play with one of the Python libraries for big data analysis: Pandas

MIT Fintech: Future commerce

I just received my MIT Fintech Future commerce certificate!🙂

It’s been a very interesting 12 week online training where I learnt about impending disruptions to the financial technologies landscape. I highly recommend it to those of you interested in fintech.

In fact I enjoyed it so much that I have now enrolled in the Big Data and Social Analytics course!😀


Adding nodes to your private blockchain

In my previous post I showed how to create your private blockchain, but a blockchain of one node is not very useful🙂 Let’s learn how to connect other nodes.

If you followed the steps of the previous post you should already have Node 1 installed. In Node 1 launch geth console and run admin.nodeInfo.enode. You should get something like this:


This will be the address that you have to give Node 2 so it can connect to Node 1

restart geth on Node 1 setting –maxpeers

geth –mine –networkid 1337 –nodiscover –maxpeers 3 console

Now install geth in Node2 and initialise it using the same genesis block you used to set up Node 1.

geth init genesisBlock.json

In order to connect Node 2 with Node 1 you need to create file static-nodes.json adding the IP and port (which need to be accessible) of Node 1’s machine.

cat > $HOME/.ethereum/static-nodes.json


run geth in Node 2, use the same network id as you did in Node 1

geth –networkid 1337 –nodiscover –verbosity 5 console

if everything has worked you will see in Node2 a message showing successful connection

I0829 22:16:38.318582 eth/handler.go:258] Peer 639d05c6307c25db [eth/63]: peer connected [Geth/v1.4.11-stable-fed692f6/linux/go1.6.2]

let’s transfer some ETH from the wallet in Node 1 to the wallet in Node 2. First create a wallet in Node 2 and save the address

> personal.newAccount()
Repeat passphrase:

in our account in Node 1 we can now send money to the newly created wallet in Node 2

>eth.sendTransaction({from:”0x55a0040fd8ac1177d598e8880cee248c7c9ac1b9″, to:”0x1329560ae07a9fc8a3161c66dfef13da609cfda5″, value:web3.toWei(5,”ether”)})

if either Node 1 or Node 2 are mining blocks you will soon see the transaction happening. You can check your new balance at your account in Node 2


Creating a private ethereum blockchain from scratch

Following this webpage  and this one (beware, some steps are deprecated), I’ve been able to create my own ethereum private blockchain. I document it here for those who would like to do the same.

Create a new user, group and home directory, for example privateeth1 and install geth for this user

sudo su
useradd privateeth1
groupadd privateeth
mkdir /home/privateeth1
chown privateeth1:privateeth /home/privateeth1
apt-get install -y build-essential libgmp3-dev golang
sudo su privateeth1
mkdir /home/privateeth1/ethereum
cd /home/privateeth1/ethereum
git clone
cd go-ethereum/
make geth

create the genesis block and initialise the blockchain

cd /home/privateeth1/ethereum/
cat > genesisBlock.json
“nonce”: “0x0000000000000042”,
“mixhash”: “0x0000000000000000000000000000000000000000000000000000000000000000”,
“difficulty”: “0x4000”,
“alloc”: {},
“coinbase”: “0x0000000000000000000000000000000000000000”,
“timestamp”: “0x00”,
“parentHash”: “0x0000000000000000000000000000000000000000000000000000000000000000”,
“extraData”: “Custom Ethereum Genesis Block”,
“gasLimit”: “0xffffffff”
go-ethereum/build/bin/geth init genesisBlock.json

start up geth in a customised port and network Id

go-ethereum/build/bin/geth –networkid 9999

open a new terminal and attach a geth console

go-ethereum/build/bin/geth attach

from within the geth console create an account and write down the address. We will initialise the amount of Ether to this account.

> personal.newAccount()

Edit the genesis block to add your account’s initial balance, afterwards initialise the blockchain again

cd /home/privateeth1/ethereum/
cat > genesisBlock.json
“nonce”: “0x0000000000000042”,
“mixhash”: “0x0000000000000000000000000000000000000000000000000000000000000000”,
“difficulty”: “0x4000”,
“alloc”: {

“write here the account address that you received from personal.newAccount(), for example 0x55a0040fd8ac1177d598e8880cee248c7c9ac1b9”:

{ “balance”:”10000000000000000000000″ }

“coinbase”: “0x0000000000000000000000000000000000000000”,
“timestamp”: “0x00”,
“parentHash”: “0x0000000000000000000000000000000000000000000000000000000000000000”,
“extraData”: “Custom Ethereum Genesis Block”,
“gasLimit”: “0xffffffff”
go-ethereum/build/bin/geth init genesisBlock.json

Now you can run geth again and you will see the balance in your account to have been updated.

go-ethereum/build/bin/geth –networkid 1234 console
> web3.fromWei(eth.getBalance(eth.coinbase),”ether”)

next step is to install geth on another computer and have them communicate. I leave that for the next post🙂

Encrypting files with GPG

One of the concerns I have in this new world of cryptocurrency wallets is that I’ve never had a file that was worth thousands of Euros! Until now the worst thing that could happen (twice) was that I could lose all my photos…

The immediate solution I imagine to make sure I don’t lose my wallet is to make many copies of it and spread them around all my computers, gdrive and dropbox. But what if some hacker gains access to the file? He could somehow crack my password and gain access to my ETH stash!

The solution I have found so far is to keep several encrypted copies of my wallet. After doing some research I like GPG (the Gnu version of PGP) which is open source and has been around for a long time. This way, if the hacker gained access to this file he would first need to crack the encryption and the Ethereum password having 2 strong layers of complexity.

I’ve installed it so far in my Windows and Mac computers and it’s pretty straight forward.

  1. Windows:
    1. Go to and download the windows executable (currently Gpg4win 2.3.2)
    2. Once it’s installed you can use the following programs:
      1. kleopatra: with this tool you can create and manage your certificates.
        1. Go to File>New Certificate>Create a personal OpenPGP key pair and follow the instructions. Don’t forget your passphrase!🙂
          1. kleopatra
        2. Once you have your private/public key pair generated you may want to share your public key with the world so they can send you encrypted messages which only you can decrypt. You can do this by right clicking on your certificate and selecting “Export Certificates…”
          1. kleopatra1
        3. A file will be generated with your public key which looks something like the below picture. Put this in your blog, email signature, billboard… you can share this public key with no risk. People can use it to send you encrypted messages. You can see my public key here
          1. kleopatra2
        4. You may also want to export your private key, to copy it to another computer on which you will want to decrypt messages. Take care to ensure your private key is not shared with anyone. To do this right click on your certificate and select “Export Secret Keys…”
          1. kleopatra3
      2. GgpEx: You can access this tool by right clicking on any file and selecting the GpgEx menu. For example to encrypt a file right click on your file (for example your Ethereum wallet) and select under the GpgEx menu>Encrypt
        1. gpgex
      3. You will now see a new file with the extension .gpg This file is encrypted and can only be decrypted by you.
      4. To decrypt it you can right click on it>GpgEx Menu>Decrypt. Insert your password and the file is decrypted.
        1. gpgex1
  2. For Mac the idea is the same, I’m using
    1. You can create new encryption keys with “GPG Keychain”. You can also copy from a different computer the private keys that you have created (in my case with the windows computer) and import them by clicking on Import.
      1. gpgmac2
    2. Once the keys are generated (or imported) you can decrypt a file by right clicking on it and selecting “Services>OpenPGP: Decrypt File”
      1. gpgpmac


Thanks to this I can now export my Ethereum wallet. Encrypt it and save a copy in my google drive, which I can download to any computer on which I have my gpg private key in case I need to send some ETH.

Password Management

I’ve taken a leap of faith into the password management world. Until a month ago I used to be the living example of how not to manage your passwords… Kevin Mitnick would not have been proud..

I’ve started using keepass, a free tool which works under windows (and Linux and Mac with mongo) and provides one place where to store all passwords. Keepass uses AES encryption to keep passwords safe. To share my passwords amongst my computers I upload my keepass file to google drive, since it’s encrypted I’m not (too) worried that someone may get all my passwords (ok, I am still a bit worried, but I guess using the same password for every service is a worse alternative, or keeping them written down in my notebook..).

I have as a pending task to investigate lastpass, safe-in-cloud and 1password (are we really sending our passwords to the cloud? one leap of faith at a time for me… ) and find a tool that works securely in ios. (Update: Keepass has Minikeepass for ios, I’ve installed it and it works. It even can get a copy of the passwords file via dropbox)