Is it possible to store ether on paper wallets or generate printable private keys offline somehow?
[Ethereum] way to generate ethereum paper wallets
cold-storagepaper-walletsSecurity
Related Solutions
Yes, you can simply generate pairs of unencrypted or encrypted private and public keys. For example, use this bulk key generator:
1,"0xb7d3a6d96960c2e9650822be7c1cc4ebe8bb3718","9a130892d949ab5faf678ac6295d3ab05a434448b824c0dc43bf86a4c2bbf747"
2,"0xbf3407c1231b3612dc6d2da07f32208ed1e17ebd","e9a1bc1d7e5a815499009cf94139b3a4f532b0530df737247b6a0eccb65e5384"
3,"0x7637dc580f362786cbdc9e59a1baa9db4b46aa38","d7c8c4735ac5d665b7d9dd4a4d3dc61f4c1bffcad9b77d0f3aee5568d6dcdd10"
4,"0x395c3f208c09a9640880ae387331d7d58123bbd1","c0f075d2aa6510f75281b19f2c43771b99248f5784503344b21c590b8003419e"
5,"0x0d59b6bc0d014ee806230c4fee77e0c83bb6f453","0da749536ce1279d99663016428fe23a3799b842f982c6a1e81fa69cc0219a45"
6,"0xad17e413f8a47a07c8c7660f5c495b20176c59e0","994c6d8e93216ebd2f1e82662c00f3a7fb3e24f1245b4571791dc369f098bf20"
7,"0xa839ecc2305f433535eb1be00fc065ef728c61df","449fcc4846ec446e996653f3be7e81cf2f9c7df072ff2ece51e9f173928fb1cd"
Which outputs CSV: ID, public key (address), private key (here: unencrypted).
You can write them down. In general, I would recommend to encrypt them with a passphrase, but the output will be much more difficult to write down:
1,"0x5a594c44c194d9269025d07b9cf95e4b8fd767d2","U2FsdGVkX18TjcT/+fNBhHk1uPh1N72Vf3CLo/vkhor2+eKSEjeFbd13PbNcx78kwfwa0Gckv5yFjjQiR0qxyApPX6Buhs5e4IsYI90llPS0t75eJOz2b7qtPKlfX28T"
2,"0x052ce0c54dd7ec93fd513688fe954ae030889e6b","U2FsdGVkX1+XJEy6O2hw1N7PGnHtpQyrlLY+xD1J2X1TlgRqUB5gnQOS6rwi/mSEbdviLCjWKc3psQuV5UikS4wOmDunlWshGNTaoMIPj51Yh0KvfW22g6Evs1Z9COo3"
3,"0xbe8467807ea1374780d56a1bf9278fc1e1f5348a","U2FsdGVkX19SHpzNamqBl/JbmW2qzddPdQpIlKBadLstvlLtjmKI9YROxZlZEnHtK4mhPrKtTUWHGEF2sLAesVkBAqD71ORbWo6cEqa+C7pm4tkInuUTWWQVGEviNmGa"
4,"0xd903ff3313fdef8126b5f38c6775c0e34577ef33","U2FsdGVkX18V+us+TZ5ebawywwbW1eDtRjv8el6adTWcqf9Ag2nzWAtKlvZytCATEge4jzPZQaYJb7dZAMgjywGmxD63BPwZu7nc4hRzd+rWdVdT3NoyDE1WGJBa47Xp"
5,"0x425c6cd22c1673084d91bdc555115cf053a128a3","U2FsdGVkX1+BRDxxc4aDdYsdzjCDmHvBwiVp7GGFeBO2fc44pE+biTTaSz52Xrm9HhcwzHyQOxQc0KpRDckTiAV0VHb6MnfWcHKxlGTt5XzoMutZYrT6DWj8refcolp2"
6,"0x47bd738c482de1017c1bb44daed1174befe599f3","U2FsdGVkX1901zVkK+GEG1PNL5LWhAM/1EGGebUVKTBEqlEesgMliEb5bSGqQF+XbgmfefXjo/1lly8tPmEKz4vS4JNQU/m9gl9KMx/TADzz+mWbYj4WVo4KIqpaRdur"
7,"0x5600370a09691dea4e81735b86fb0b76182dcdee","U2FsdGVkX1+RwHwIB6SfPMAsoBGyWoz9QO72YY+J3hcfqWvlVnlW68jd5qAOaRVlZgnywpiKJmGjDCrTNR/ZiN0pHj3YlVN3+WdJ13qhFiMBxdLkrifblcNi+mXMCKm4"
A good alternative might a brain wallet, where you just have to remember the 20 words to generate the key pair. Here is one generator. Here is another (click "get address").
But as always, test this with small amounts first!
We at MyEtherWallet.com implemented an offline transaction tool to do exactly this. While most people who are cold-storage fanatics know command line and the inner-workings of gas price and nonce, this allows you to do it via GUI.
Navigate to the "Offline Transaction" tab via your online computer. Here you will generate the current gas price and nonce.
Enter the FROM address in the field. Please note, this is the address you are sending FROM, not TO. This generates the nonce and gas price.
Move to your offline computer. Enter the TO ADDRESS and the AMOUNT you wish to send.
Enter the GAS PRICE as it was displayed to you on your online computer in step #1.
The GAS LIMIT has a default value of 21000. This will cover a standard transaction. If you are sending to a contract or are including additional data with your transaction, you will need to increase the gas limit. Any excess gas will be returned to you.
Enter the NONCE as it was displayed to you on your online computer in step #1. If you wish, enter some data. Data is optional. If you enter data, you will need to include more than the 21000 default gas limit. All data is in HEX format. Select your wallet file -or- enter/paste your private key and unlock your wallet.
Press the "GENERATE SIGNED TRANSACTION" button.
The field below this button will populate with your singed transaction. Copy this and move it back to your online computer, or you can use the QR code provided.
On your online computer, paste the signed transaction into the text field in Step 3 and click "SEND TRANSACTION". This will broadcast your transaction.
Alternatively, you could use other services in order to broadcast the signed transaction. Etherscan has a field you can use to broadcast transactions.
drcode on reddit made a tool to decode a signed transaction so you can verify it's doing what it says it is doing.
FYI, everything on MyEtherWallet is almost 100% offline. The only thing that leaves your computer while sending is the signed transaction, which is generated by your browser. We also receive the nonce and gas price, which is why you must generate those bits of information online.
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Best Answer
Cold storage has been discussed in the past on Ethereum's subreddit.
Just to give my 2 cents, on Ubuntu I use the following on the command line:
Add option
-l Hto get a code that is easier to decode. Theqrencodetool uses the open sourcelibqrencodelibrary, and can be installed using:Once you have the image file, you can then print it off. (Using a wired connection to a printer, unless you're happy with the printer's levels of wireless security.)
A command line tool to decode a scanned QR code or image file is included in the zbar-tools package, e.g.
zbarimg --quiet qr_image.pngThe general disclaimer: You'll need to ensure you're happy with piping your keys into someone else's utility... The source code is available, but you'd need to be familiar enough with C to be able to check it isn't taking a copy of the key and then sending it back to the mothership.