Public Key & Bitcoin Adresse

Uli · 28. Oktober 2021 um 18:34

Wenn ich es richtig verstanden habe ist das das selbe?
Irgendwo habe ich gelesen das man evtl anhand des public key den privat key ermitteln könnte, das wäre sehr unschön, andererseits wurden letztens doch Bitcoin versteigert wo auf dem Zertifikat die Adresse draufstand🤔
Evtl kann wer Licht ins Dunkel bringen😅

Nessaiy · 28. Oktober 2021 um 18:37

Es gibt glaub ich einen Unterschied zwischen Public Key und Adresse. Der Public Key wird mit der ersten rausgehenden Transaktion veröffentlicht.
Deswegen soll man adressen nicht mehrmals benutzen.
Aber selbst fürs herleiten des private key aus dem public key muss der sha256 hash einmal rückgerechnet werden. Von der Adresse sogar zweimal.

TrailSlave · 28. Oktober 2021 um 18:38

Nein das ist nicht das selbe.

Die Public Adress wird aus dem Public key abgeleitet.

Es ist nicht möglich aus dem Public Key den Private Key zu errechnen.

SHA-2 · 28. Oktober 2021 um 18:50

github.com

bitcoinbook/bitcoinbook/blob/develop/ch04.asciidoc

[[ch04_keys_addresses]]
== Keys, Addresses

((("cryptography", "defined")))((("cryptography", see="also keys and addresses")))You may have heard that bitcoin is based on _cryptography_, which is a branch of mathematics used extensively in computer security. Cryptography means "secret writing" in Greek, but the science of cryptography encompasses more than just secret writing, which is referred to as encryption. Cryptography can also be used to prove knowledge of a secret without revealing that secret (digital signature), or prove the authenticity of data (digital fingerprint). These types of cryptographic proofs are the mathematical tools critical to bitcoin and used extensively in bitcoin applications. ((("encryption")))((("encryption", see="also keys and addresses")))Ironically, encryption is not an important part of bitcoin, as its communications and transaction data are not encrypted and do not need to be encrypted to protect the funds. In this chapter we will introduce some of the cryptography used in bitcoin to control ownership of funds, in the form of keys, addresses, and wallets.

=== Introduction

((("digital keys", see="keys and addresses")))((("keys and addresses", "overview of", id="KAover04")))((("digital signatures", "purpose of")))Ownership of bitcoin is established through _digital keys_, _Bitcoin addresses_, and _digital signatures_. The digital keys are not actually stored in the network, but are instead created and stored by users in a file, or simple database, called a _wallet_. The digital keys in a user's wallet are completely independent of the Bitcoin protocol and can be generated and managed by the user's wallet software without reference to the blockchain or access to the internet. Keys enable many of the interesting properties of bitcoin, including decentralized trust and control, ownership attestation, and the cryptographic-proof security model.

Most bitcoin transactions require a valid digital signature to be included in the blockchain, which can only be generated with a secret key; therefore, anyone with a copy of that key has control of the bitcoin. ((("witnesses")))The digital signature used to spend funds is also referred to as a _witness_, a term used in cryptography. The witness data in a bitcoin transaction testifies to the true ownership of the funds being spent.

((("public and private keys", "key pairs")))((("public and private keys", see="also keys and addresses")))Keys come in pairs consisting of a private (secret) key and a public key. Think of the public key as similar to a bank account number and the private key as similar to the secret PIN, or signature on a check, that provides control over the account. These digital keys are very rarely seen by the users of bitcoin. For the most part, they are stored inside the wallet file and managed by the bitcoin wallet software.

In the payment portion of a bitcoin transaction, the recipient's public key is represented by its digital fingerprint, called a _Bitcoin address_, which is used in the same way as the beneficiary name on a check (i.e., "Pay to the order of"). In most cases, a Bitcoin address is generated from and corresponds to a public key. However, not all Bitcoin addresses represent public keys; they can also represent other beneficiaries such as scripts, as we will see later in this chapter. This way, Bitcoin addresses abstract the recipient of funds, making transaction destinations flexible, similar to paper checks: a single payment instrument that can be used to pay into people's accounts, pay into company accounts, pay for bills, or pay to cash. The Bitcoin address is the only representation of the keys that users will routinely see, because this is the part they need to share with the world.

First, we will introduce cryptography and explain the mathematics used in bitcoin. Next, we will look at how keys are generated, stored, and managed.  We will review the various encoding formats used to represent private and public keys, addresses, and script addresses. Finally, we will look at advanced use of keys and addresses: vanity, multisignature, and script addresses and paper wallets.

==== Public Key Cryptography and Cryptocurrency

((("keys and addresses", "overview of", "public key cryptography")))((("digital currencies", "cryptocurrency")))Public key cryptography was invented in the 1970s and is a mathematical foundation for computer and information security.

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Kurz: Nein du kannst den private key nicht aus dem public key „reverse engineeren“ / ableiten.

sutterseba · 28. Oktober 2021 um 19:15

Das ist sehr übertrieben ausgedrückt.

Man verliert nur theoretische Sicherheit durch das veröffentlichen einer Signatur. Das ist heute aber absolut vernachlässigbar.

Eine Adresse ist einfach ein (Base58Check) Hash (SHA256 + RIPEMD160) des Public Keys. Man „verliert“ also die zusätzliche Sicherheit der Hashfunktion - was nicht bedeutet dass man sich darüber Sorgen machen sollte.

Der Hauptgrund Adressen nicht mehrmals zu benutzen sollte die Privatsphäre sein. Der Schutz des Public Keys ist nur ein minimaler Nebeneffekt davon.

Bei Adressen die man sehr lange nutzen will (und man etwas paranoid ist) kann es sinnvoll sein darauf zu achten.

Der Public Key ist kein Hash des Private Keys!

Wenn du verstehen willst wie das genau funktioniert dann wirst du über den Link oben fündig.

Muss man aber nicht verstehen, alles was du wissen musst: Extrem sicher.

Kann man. Wenn du genug Zeit & Geld mitbringst.

(Musst mehrere Zeitalter unseres Universums einplanen…)

Nessaiy · 28. Oktober 2021 um 19:19

Ok, dann wars zuerst die ECM, danach die hashing. Hatte noch im Kopf, dass das jeweils von einander abgeleitet wird.

SHA-2 · 28. Oktober 2021 um 19:20

@sutterseba man könnte natürlich auch sagen, Stand heute, nicht möglich! Das Modell ist schon sehr theoretisch.

renna · 28. Oktober 2021 um 20:08

Einfach mal auf Blocktrainer.de vorbei schauen