Compressed address bitcoin

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btc-address-dump 0.1.8

Asked 9 years ago. Active 3 years, 3 months ago. Viewed 30k times. The standard Bitcoin client in version 0. Improve this question. Thilo Thilo 4, 4 4 gold badges 23 23 silver badges 36 36 bronze badges. Add a comment. Active Oldest Votes. Improve this answer.

David Schwartz David Schwartz No, it can't. But it is always disallowed to try to read a wallet. That's a permitted break. You could still manually extract the case, uncompress them, and put them into the earlier form if you had to. But that kind of compatibility is not supported.

You can't go back with a newer wallet file unless you translate the data. To answer your other question, only in the wallet. Compressed keys aren't yet supported anywhere else because that would be a protocol-breaking change.

4. Keys, Addresses - Mastering Bitcoin, 2nd Edition [Book]

The advantage is mainly for the blockchain and the network, as transactions will be a bit smaller now. It's 33 bytes instead of 65, by the way. I have a problem understanding it : I have an uncompressed private key, I enter it in bitaddress. On one I have one million dollar, on the other 0. And they both come from the same private key. How does that make sense?

Show 6 more comments. Jus12 1, 1 1 gold badge 12 12 silver badges 24 24 bronze badges. I hope this helps future readers contrast the two answers here. The public key is calculated from the private key using elliptic curve multiplication, which is irreversible: where k is the private key, G is a constant point called the generator point and K is the resulting public key. Elliptic curve cryptography is a type of asymmetric or public-key cryptography based on the discrete logarithm problem as expressed by addition and multiplication on the points of an elliptic curve.

Figure is an example of an elliptic curve, similar to that used by bitcoin. Bitcoin uses a specific elliptic curve and set of mathematical constants, as defined in a standard called secpk1 , established by the National Institute of Standards and Technology NIST. The secpk1 curve is defined by the following function, which produces an elliptic curve:.

Because this curve is defined over a finite field of prime order instead of over the real numbers, it looks like a pattern of dots scattered in two dimensions, which makes it difficult to visualize. However, the math is identical as that of an elliptic curve over the real numbers. As an example, Figure shows the same elliptic curve over a much smaller finite field of prime order 17, showing a pattern of dots on a grid.

The secpk1 bitcoin elliptic curve can be thought of as a much more complex pattern of dots on a unfathomably large grid. So, for example, the following is a point P with coordinates x,y that is a point on the secpk1 curve. You can check this yourself using Python:. Geometrically, this third point P 3 is calculated by drawing a line between P 1 and P 2. This line will intersect the elliptic curve in exactly one additional place. This tangent will intersect the curve in exactly one new point. You can use techniques from calculus to determine the slope of the tangent line.

These techniques curiously work, even though we are restricting our interest to points on the curve with two integer coordinates! In some cases i. This shows how the point at infinity plays the role of 0. Now that we have defined addition, we can define multiplication in the standard way that extends addition.

Starting with a private key in the form of a randomly generated number k , we multiply it by a predetermined point on the curve called the generator point G to produce another point somewhere else on the curve, which is the corresponding public key K. The generator point is specified as part of the secpk1 standard and is always the same for all keys in bitcoin:. Because the generator point is always the same for all bitcoin users, a private key k multiplied with G will always result in the same public key K. The relationship between k and K is fixed, but can only be calculated in one direction, from k to K.

A private key can be converted into a public key, but a public key cannot be converted back into a private key because the math only works one way. Implementing the elliptic curve multiplication, we take the private key k generated previously and multiply it with the generator point G to find the public key K:. To visualize multiplication of a point with an integer, we will use the simpler elliptic curve over the real numbers—remember, the math is the same.

Our goal is to find the multiple kG of the generator point G. That is the same as adding G to itself, k times in a row. In elliptic curves, adding a point to itself is the equivalent of drawing a tangent line on the point and finding where it intersects the curve again, then reflecting that point on the x-axis. Figure shows the process for deriving G, 2G, 4G, as a geometric operation on the curve. Most bitcoin implementations use the OpenSSL cryptographic library to do the elliptic curve math. A bitcoin address is a string of digits and characters that can be shared with anyone who wants to send you money.

Because paper checks do not need to specify an account, but rather use an abstract name as the recipient of funds, that makes paper checks very flexible as payment instruments. Bitcoin transactions use a similar abstraction, the bitcoin address, to make them very flexible.

The bitcoin address is derived from the public key through the use of one-way cryptographic hashing.

Bitcoin compressed and uncompressed addresses

Cryptographic hash functions are used extensively in bitcoin: in bitcoin addresses, in script addresses, and in the mining proof-of-work algorithm. A bitcoin address is not the same as a public key. Bitcoin addresses are derived from a public key using a one-way function. Base58Check is also used in many other ways in bitcoin, whenever there is a need for a user to read and correctly transcribe a number, such as a bitcoin address, a private key, an encrypted key, or a script hash. In the next section we will examine the mechanics of Base58Check encoding and decoding, and the resulting representations.

Figure illustrates the conversion of a public key into a bitcoin address. In order to represent long numbers in a compact way, using fewer symbols, many computer systems use mixed-alphanumeric representations with a base or radix higher than For example, whereas the traditional decimal system uses the 10 numerals 0 through 9, the hexadecimal system uses 16, with the letters A through F as the six additional symbols.

A number represented in hexadecimal format is shorter than the equivalent decimal representation. Base is most commonly used to add binary attachments to email. Base58 is a text-based binary-encoding format developed for use in bitcoin and used in many other cryptocurrencies. It offers a balance between compact representation, readability, and error detection and prevention. Base58 is a subset of Base64, using the upper- and lowercase letters and numbers, but omitting some characters that are frequently mistaken for one another and can appear identical when displayed in certain fonts.

Or, more simply, it is a set of lower and capital letters and numbers without the four 0, O, l, I just mentioned.

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To add extra security against typos or transcription errors, Base58Check is a Base58 encoding format, frequently used in bitcoin, which has a built-in error-checking code. The checksum is an additional four bytes added to the end of the data that is being encoded. The checksum is derived from the hash of the encoded data and can therefore be used to detect and prevent transcription and typing errors. When presented with a Base58Check code, the decoding software will calculate the checksum of the data and compare it to the checksum included in the code. If the two do not match, that indicates that an error has been introduced and the Base58Check data is invalid.

For example, this prevents a mistyped bitcoin address from being accepted by the wallet software as a valid destination, an error that would otherwise result in loss of funds. For example, in the case of a bitcoin address the prefix is zero 0x00 in hex , whereas the prefix used when encoding a private key is 0x80 in hex. A list of common version prefixes is shown in Table From the resulting byte hash hash-of-a-hash , we take only the first four bytes.

These four bytes serve as the error-checking code, or checksum. The checksum is concatenated appended to the end. The result is composed of three items: a prefix, the data, and a checksum. This result is encoded using the Base58 alphabet described previously. Figure illustrates the Base58Check encoding process. In bitcoin, most of the data presented to the user is Base58Check-encoded to make it compact, easy to read, and easy to detect errors.

The version prefix in Base58Check encoding is used to create easily distinguishable formats, which when encoded in Base58 contain specific characters at the beginning of the Base58Check-encoded payload.

Why is the elliptic curve used?

These characters make it easy for humans to identify the type of data that is encoded and how to use it. This is what differentiates, for example, a Base58Check-encoded bitcoin address that starts with a 1 from a Base58Check-encoded private key WIF format that starts with a 5. Some example version prefixes and the resulting Base58 characters are shown in Table The code example uses the libbitcoin library introduced in Alternative Clients, Libraries, and Toolkits for some helper functions.

The code uses a predefined private key so that it produces the same bitcoin address every time it is run, as shown in Example Both private and public keys can be represented in a number of different formats. These representations all encode the same number, even though they look different. These formats are primarily used to make it easy for people to read and transcribe keys without introducing errors.

The private key can be represented in a number of different formats, all of which correspond to the same bit number. Table shows three common formats used to represent private keys.