Address: defined in CryptoCurrency

Understand that an Address: defined in CryptoCurrency; is a string of letters, and-or numbers that is publicly available and allows cryptocurrency to be received, held and sent.

--------------------------

A Bitcoin address, or simply address, is an identifier of 26-35 alphanumeric characters, beginning with the number 1, 3 or bc1 that represents a possible destination for a bitcoin payment. Addresses can be generated at no cost by any user of Bitcoin. For example, using Bitcoin Core, one can click "New Address" and be assigned an address. It is also possible to get a Bitcoin address using an account at an exchange or online wallet service.
There are currently three address formats in use:

P2PKH which begin with the number 1, eg: 1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2.
P2SH type starting with the number 3, eg: 3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy.
Bech32 type starting with bc1, eg: bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq.

List of address prefixes

Blockchain-based currencies use encoded strings, which are in a Base58Check encoding with the exception of Bech32 encodings. The encoding includes a prefix (traditionally a single version byte), which affects the leading symbol(s) in the encoded result. The following is a list of some prefixes which are in use in the reference Bitcoin codebase.

Decimal prefix	Hex	Example use	Leading symbol(s)	Example
0	00	Pubkey hash (P2PKH address)	1	`17VZNX1SN5NtKa8UQFxwQbFeFc3iqRYhem`
5	05	Script hash (P2SH address)	3	`3EktnHQD7RiAE6uzMj2ZifT9YgRrkSgzQX`
128	80	Private key (WIF, uncompressed pubkey)	5	`5Hwgr3u458GLafKBgxtssHSPqJnYoGrSzgQsPwLFhLNYskDPyyA`
128	80	Private key (WIF, compressed pubkey)	K or L	`L1aW4aubDFB7yfras2S1mN3bqg9nwySY8nkoLmJebSLD5BWv3ENZ`
4 136 178 30	0488B21E	BIP32 pubkey	xpub	`xpub661MyMwAqRbcEYS8w7XLSVeEsBXy79zSzH1J8vCdxAZningWLdN3zgtU6LBpB85b3D2yc8sfvZU521AAwdZafEz7mnzBBsz4wKY5e4cp9LB`
4 136 173 228	0488ADE4	BIP32 private key	xprv	`xprv9s21ZrQH143K24Mfq5zL5MhWK9hUhhGbd45hLXo2Pq2oqzMMo63oStZzF93Y5wvzdUayhgkkFoicQZcP3y52uPPxFnfoLZB21Teqt1VvEHx`
111	6F	Testnet pubkey hash	m or n	`mipcBbFg9gMiCh81Kj8tqqdgoZub1ZJRfn`
196	C4	Testnet script hash	2	`2MzQwSSnBHWHqSAqtTVQ6v47XtaisrJa1Vc`
239	EF	Testnet Private key (WIF, uncompressed pubkey)	9	`92Pg46rUhgTT7romnV7iGW6W1gbGdeezqdbJCzShkCsYNzyyNcc`
239	EF	Testnet Private key (WIF, compressed pubkey)	c	`cNJFgo1driFnPcBdBX8BrJrpxchBWXwXCvNH5SoSkdcF6JXXwHMm`
4 53 135 207	043587CF	Testnet BIP32 pubkey	tpub	`tpubD6NzVbkrYhZ4WLczPJWReQycCJdd6YVWXubbVUFnJ5KgU5MDQrD998ZJLNGbhd2pq7ZtDiPYTfJ7iBenLVQpYgSQqPjUsQeJXH8VQ8xA67D`
4 53 131 148	04358394	Testnet BIP32 private key	tprv	`tprv8ZgxMBicQKsPcsbCVeqqF1KVdH7gwDJbxbzpCxDUsoXHdb6SnTPYxdwSAKDC6KKJzv7khnNWRAJQsRA8BBQyiSfYnRt6zuu4vZQGKjeW4YF`
		Bech32 pubkey hash or script hash	bc1	`bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4`
		Bech32 testnet pubkey hash or script hash	tb1	`tb1qw508d6qejxtdg4y5r3zarvary0c5xw7kxpjzsx`

Note: that private keys for compressed and uncompressed bitcoin public keys use the same version byte. The reason for the compressed form starting with a different character is because a 0x01 byte is appended to the private key before base58 encoding.

The following table shows the leading symbol(s) and address length(s) for 160 bit hashes for each of the possible decimal version values:

Decimal version	Leading symbol	Address length
0	1	up to 34
1	Q-Z, a-k, m-o	33
2	o-z, 2	33 or 34
3	2	34
4	2 or 3	34
5-6	3	34
7	3 or 4	34
8	4	34
9	4 or 5	34
10-11	5	34
12	5 or 6	34
13	6	34
14	6 or 7	34
15-16	7	34
17	7 or 8	34
18	8	34
19	8 or 9	34
20-21	9	34
22	9 or A	34
23	A	34
24	A or B	34
25-26	B	34
27	B or C	34
28	C	34
29	C or D	34
30-31	D	34
32	D or E	34
33	E	34
34	E or F	34
35-36	F	34
37	F or G	34
38	G	34
39	G or H	34
40-41	H	34
42	H or J	34
43	J	34
44	J or K	34
45-46	K	34
47	K or L	34
48	L	34
49	L or M	34
50-51	M	34
52	M or N	34
53	N	34
54	N or P	34
55-56	P	34
57	P or Q	34
58	Q	34
59	Q or R	34
60-61	R	34
62	R or S	34
63	S	34
64	S or T	34
65-66	T	34
67	T or U	34
68	U	34
69	U or V	34
70-71	V	34
72	V or W	34
73	W	34
74	W or X	34
75-76	X	34
77	X or Y	34
78	Y	34
79	Y or Z	34
80-81	Z	34
82	Z or a	34
83	a	34
84	a or b	34
85	b	34
86	b or c	34
87-88	c	34
89	c or d	34
90	d	34
91	d or e	34
92-93	e	34
94	e or f	34
95	f	34
96	f or g	34
97-98	g	34
99	g or h	34
100	h	34
101	h or i	34
102-103	i	34
104	i or j	34
105	j	34
106	j or k	34
107-108	k	34
109	k or m	34
110	m	34
111	m or n	34
112-113	n	34
114	n or o	34
115	o	34
116	o or p	34
117-118	p	34
119	p or q	34
120	q	34
121	q or r	34
122-123	r	34
124	r or s	34
125	s	34
126	s or t	34
127-128	t	34
129	t or u	34
130	u	34
131	u or v	34
132-133	v	34
134	v or w	34
135	w	34
136	w or x	34
137-138	x	34
139	x or y	34
140	y	34
141	y or z	34
142-143	z	34
144	z or 2	34 or 35
145-255	2	35

References

https://github.com/bitcoin/bitcoin/blob/0.14/src/chainparams.cpp#L129-L131

https://github.com/bitcoin/bitcoin/blob/0.14/src/chainparams.cpp#L229-L231

https://github.com/bitcoin/bitcoin/blob/0.14/src/chainparams.cpp#L325-L327

A Bitcoin address is a single-use token

Like e-mail addresses, you can send bitcoins to a person by sending bitcoins to one of their addresses. However, unlike e-mail addresses, people have many different Bitcoin addresses and a unique address should be used for each transaction. Most Bitcoin software and websites will help with this by generating a brand new address each time you create an invoice or payment request.

Addresses can be created offline

Creating addresses can be done without an Internet connection and does not require any contact or registration with the Bitcoin network. It is possible to create large batches of addresses offline using freely available software tools. Generating batches of addresses is useful in several scenarios, such as e-commerce websites where a unique pre-generated address is dispensed to each customer who chooses a "pay with Bitcoin" option. Newer "HD wallets" can generate a "master public key" token which can be used to allow untrusted systems (such as webservers) to generate an unlimited number of addresses without the ability to spend the bitcoins received.

Addresses are often case sensitive and exact

Old-style Bitcoin addresses are case-sensitive. Bitcoin addresses should be copied and pasted using the computer's clipboard wherever possible. If you hand-key a Bitcoin address, and each character is not transcribed exactly - including capitalization - the incorrect address will most likely be rejected by the Bitcoin software. You will have to check your entry and try again.
The probability that a mistyped address is accepted as being valid is 1 in 2³², that is, approximately 1 in 4.29 billion.
New-style bech32 addresses are case insensitive.

Proving you receive with an address

Most Bitcoin wallets have a function to "sign" a message, proving the entity receiving funds with an address has agreed to the message. This can be used to, for example, finalise a contract in a cryptographically provable way prior to making payment for it.
Some services will also piggy-back on this capability by dedicating a specific address for authentication only, in which case the address should never be used for actual Bitcoin transactions. When you login to or use their service, you will provide a signature proving you are the same person with the pre-negotiated address.
It is important to note that these signatures only prove one receives with an address. Since Bitcoin transactions do not have a "from" address, you cannot prove you are the sender of funds.
Current standards for message signatures are only compatible with "version zero" bitcoin addresses (that begin with the number 1).

Address validation

If you would like to validate a Bitcoin address in an application, it is advisable to use a method from this thread rather than to just check for string length, allowed characters, or that the address starts with a 1 or 3. Validation may also be done using open source code available in various languages or with an online validating tool.

Multi-signature addresses

Addresses can be created that require a combination of multiple private keys. Since these take advantage of newer features, they begin with the newer prefix of 3 instead of the older 1. These can be thought of as the equivalent of writing a check to two parties - "pay to the order of somebody AND somebody else" - where both parties must endorse the check in order to receive the funds.
The actual requirement (number of private keys needed, their corresponding public keys, etc.) that must be satisfied to spend the funds is decided in advance by the person generating this type of address, and once an address is created, the requirement cannot be changed without generating a new address.

What's in an address

Most Bitcoin addresses are 34 characters. They consist of random digits and uppercase and lowercase letters, with the exception that the uppercase letter "O", uppercase letter "I", lowercase letter "l", and the number "0" are never used to prevent visual ambiguity.
Some Bitcoin addresses can be shorter than 34 characters (as few as 26) and still be valid. A significant percentage of Bitcoin addresses are only 33 characters, and some addresses may be even shorter. Every Bitcoin address stands for a number. These shorter addresses are valid simply because they stand for numbers that happen to start with zeroes, and when the zeroes are omitted, the encoded address gets shorter.
Several of the characters inside a Bitcoin address are used as a checksum so that typographical errors can be automatically found and rejected. The checksum also allows Bitcoin software to confirm that a 33-character (or shorter) address is in fact valid and isn't simply an address with a missing character.

Testnet

Addresses on the Bitcoin Testnet are generated with a different address version, which results in a different prefix.

Misconceptions

Address reuse

Addresses are not intended to be used more than once, and doing so has numerous problems associated.

Address balances

Addresses are not wallets nor accounts, and do not carry balances. They only receive funds, and you do not send "from" an address at any time. Various confusing services and software display bitcoins received with an address, minus bitcoins sent in random unrelated transactions as an "address balance", but this number is not meaningful: it does not imply the recipient of the bitcoins sent to the address has spent them, nor that they still have the bitcoins received.
An example of bitcoin loss resulting from this misunderstanding is when people believed their address contained 3btc. They spent 0.5btc and believed the address now contained 2.5btc when actually it contained zero. The remaining 2.5btc was transferred to a change address which was not backed up and therefore lost. This has happened on a few occasions to users of Paper wallets.

"From" addresses

Bitcoin transactions do not have any kind of origin-, source- or "from" address.

Anti-AdBlocker

Thursday, August 2, 2018

Address: defined in CryptoCurrency