Bitcoin is protected by two forms of cryptography

If you use a poor source of entropy for the signatures, then reusing the same bitcoin address will let someone deduce the private key. An Android RNG bug caused the theft of a bunch of bitcoins in this manner. If the victims had always used new change addresses, their coins would have been safe.

This is because a bitcoin is protected by two forms of cryptography: the Elliptic Curve Digital Signature Algorithm (ECDSA) and a hash of the public key.

Public keys are broadcast only when spending to match the signature. As long as you have never spent bitcoins, all people know is the RIPEMD160 hash of the SHA256 hash of the public key.

To crack a bitcoin you need to break both forms of cryptography, breaking either one on its own is very hard (if good RNG is used), breaking both at the same time is exponentially harder.

When you use a bitcoin you have to expose the public key, this means you are now only protected by one form of cryptography (ECDSA).

Comments

Post a Comment

Popular posts from this blog

Do not use (only) flash memory (SSD drives, hardware wallets, USB flash drives) for your precious private keys!

Image
Flash memory is not a reliable medium for archives. Especially when there is no regular power. I have personal experience with usb flash drive not powered for weeks - one file became corrupted . (Read more here: Archiving private keys - TLDR version. ) You should always back up on paper and other mediums. Flash memory is prone to failure if it is not powered for weeks or more and if there are ionizing radiation When you write your precious private keys you should use technologies like Parchive and ZFS . And make several copies of your files. It's OK if you use your USB flash drive for another backup, but don't rely on it! Always back up on DVDs (even small files!), paper and online (after encryption with CPU and RAM intensive key derivative function like scrypt). Here is example of using the scrypt utility: $ sudo apt-get install scrypt $ scrypt enc -M 1073741824 -t 200 secret.txt encrypted.scrypt Do not use default values of "-M" and "-t", they...
Read more

Archiving private keys - TLDR version

0. Make multiple encrypted copies. On DVDs (they are better than CDs and Blu-Ray discs; DVD+R are better than DVD-R), paper, cloud services like DropBox, OneDrive, Google Drive, e-mail it to yourself and to your friends, use P2P storage services like MaidSafe, Storj and Sia , etc. 1. Use proper font when printing PGP encrypted keys on paper. 2. Flash memory (SSD, USB flash drives, hardware wallets) is less reliable when not powered regularly (i.e. every week). 3. Use error correction methods like Parchive and ZFS. 4. Print on paper or store on digital media only encrypted data. 5. Your encryption software should use CPU/RAM-intensive KDF (i.e. scrypt with secure options - do not use defaults! ). First, encrypt with scrypt and then encrypt it again with PGP (using different password!) in ASCII armor mode before print it (other methods like QR codes may not be reliable as multiple copies of the PGP ASCII armor). Do not use the same password for the PGP because it's easy to brute...
Read more
[ad removed]