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Ethereum-109 MyEtherWallet signed message, signature

With MyEtherWallet, you can send a message (with your signature on it) to your friend, and your friend can be sure that the message was sent by you (by verifying the signature).

Step 1: Create your own wallet using MyEtherWallet and keep both keys.
I use the following for demonstration:

Private key (PrK) 05f7b61d8ebb7111be30c28c105b17c1a19e20a9a189d9a05f452f1fdf4e56c4
Address (Adr) 0x9687A96cd4699D3B181d592c15BE8D842891DB56

Let’s say A will send a signed message to B
Then A keeps PrK and B keeps Adr
(B will know “0x9687A96cd4699D3B181d592c15BE8D842891DB56” is A’s address)

Step 2: Create a signed message
Open webpage
Access your wallet using the above Prk

Type the message:

It’s urgent, please deposit HK$50,000 in my account XXX-XXX-XXX

Press “Sign Message”,you will get the following

{
“address”: “0x9687a96cd4699d3b181d592c15be8d842891db56”,
“msg”: “It’s urgent, please deposit HK$50,000 in my account XXX-XXX-XXX”,
“sig”: “0xb4989cb90b433fc05b96ce54a6b7317244b1f9c4f6bea5c5efbadff3025ed5613181e02ca9dff97c7680c603bb63790869ceabca42569f29a646a0fef24820131b”,
“version”: “2”
}

Step 3: Send out the following by E-mail, Whatsapp or ….

It’s urgent, please deposit HK$50,000 in my account XXX-XXX-XXX

0xb4989cb90b433fc05b96ce54a6b7317244b1f9c4f6bea5c5efbadff3025ed5613181e02ca9dff97c7680c603bb63790869ceabca42569f29a646a0fef24820131b

Step 4: B Verify the signature
Open webpage
Fill in as shown in the video
Press verify, that’s it.
The message is 100% from A (or anyone holding the Private Key)
If someone sends the message without the correct signature, B cannot verify it.

Step 2a: Sign message using an offline mobile
Bookmark this “file:///storage/emulated/0/MEW/signmsg.html” in mobile
Open the above webpage
(you should have a copy of the MyEtherWallet web-site as shown in 107)
If you have a QR-code of the private key in the mobile, use QR-Droid to get it.
Access your wallet using the private key
Type in the message
Press “Sign Message”, Signature appears

To move the above signature to online device, here’s the trick
1. copy the signature
2. open “file:///storage/emulated/0/MEW/index.html#offline-transaction”
3. paste the signature in “Signed Transaction”, you will have a QR-code
(MyEtherWallet can generate the QR-code for any text in the box)
4. scan the QR-code using online mobile or computer, you then have the signature

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