You should never send iota to an address that was already spent. This will make it possible for an attacker to steal your iotas. This rule is uninfluenced by any snapshot.
The problem after a snapshot is, that every node deletes the transaction history, only the balances are saved. Usually your wallet doesn't show any spent addresses anymore (thus ...
Simplified, Lamport One-Time-Signatures (OTS) work as follows. For illustration purposes I am using Bits and not Trits.
Assume you have a private key PRIV that consists of 100 (random) pairs of numbers, so a total of 200. To create your public key PUB you hash each of these 200 numbers, giving you a new sequence of 100 pairs.
Now if you want to sign any ...
One of the reasons is quantum-security.
Traditional cryptocurrencies base their security on elliptic-curve cryptography. Classical examples of such algorithms are the RSA Cryptosystem, Diffie-Hellman Key Exchange or Digital Signature Algorithm, all of which are known to be vulnerable to quantum computers. Winternitz hash-based signatures, on the other hand, ...
All hashes in the signing function use Kerl.
We start from an 81 tryte subseed that is generated by taking Kerl(seed + index). This will make the subseed sufficiently independent so that it is impossible to figure out the original seed used to generate the list of addresses.
The private key length depends on the security level S, which can be 1, 2, or 3.
Firstly, it is to be quantum-secure:
And secondly because there aren't many alternative quantum-secure signature schemes to begin with:
How to get iota out of an address that has already been used twice?
use the CLI wallet https://github.com/iotaledger/cli-app to avoid the "key reuse" error
Is it possible to get IOTAs safely out of an address from which two or more transactions were made already?
If you spent some funds from an address, the address is already not safe to keep anymore ...
The seed itself is still safe to use, the one time signature weakening occurs only for that specific address (you leak part of the private key "paired" with the address itself, not part of your seed).
After a snapshot, you keep reattaching addresses (from index 0 upwards) until you arrive to an address that contains some iotas. If you always follow the rule ...