Address format for Bitcoin Cash

Abstract

This document describes a proposed address format to be used on Bitcoin Cash. It is a base32 encoded format using BCH[1] codes as checksum and that can be used directly in links or QR codes.

This format reuses the work done for Bech32[2] and is similar in some aspects, but improves on others.

Specification

The address is composed of

  1. A prefix indicating the network on which this address is valid.
  2. A separator, always :
  3. A base32 encoded payload indicating the destination of the address and containing a checksum.

Prefix

The prefix indicates the network on which this addess is valid. It is set to bitcoincash for Bitcoin Cash main net, bchtest for bitcoin cash testnet and bchreg for bitcoin cash regtest.

The prefix is followed by the separator :.

When presented to users, the prefix may be omitted as it is part of the checksum computation. The checksum ensures that addresses on different networks will remain incompatible, even in the absence of an explicit prefix.

Payload

The payload is a base32 encoded stream of data.

01234567
+0qpzry9x8
+8gf2tvdw0
+16s3jn54kh
+24ce6mua7l

The payload is composed of 3 elements:

  1. A version byte indicating the type of address.
  2. A hash.
  3. A 40 bits checksum.

Version byte

The version byte's most signficant bit is reserved and must be 0. The 4 next bits indicate the type of address and the 3 least significant bits indicate the size of the hash.

Size bitsHash size in bits
0160
1192
2224
3256
4320
5384
6448
7512

Encoding the size of the hash in the version field ensure that it is possible to check that the length of the address is correct.

Type bitsMeaningVersion byte value
0P2KH0
1P2SH8

Further types will be added as new features are added.

Hash

The hash part really deserves not much explanation as its meaning is dependent on the version field. It is the hash that represents the data, namely a hash of the public key for P2KH and the hash of the reedemScript for P2SH.

Checksum

The checksum is a 40 bits BCH codes defined over GF(2^5). It ensures the detection of up to 6 errors in the address and 8 in a row. Combined with the length check, this provides very strong guarantee against errors.

The checksum is computed per the code below:

uint64_t PolyMod(const data &v) {
    uint64_t c = 1;
    for (uint8_t d : v) {
        uint8_t c0 = c >> 35;
        c = ((c & 0x07ffffffff) << 5) ^ d;

        if (c0 & 0x01) c ^= 0x98f2bc8e61;
        if (c0 & 0x02) c ^= 0x79b76d99e2;
        if (c0 & 0x04) c ^= 0xf33e5fb3c4;
        if (c0 & 0x08) c ^= 0xae2eabe2a8;
        if (c0 & 0x10) c ^= 0x1e4f43e470;
    }

    return c ^ 1;
}

The checksum is calculated over the following data (list of integers in range 0-31):

  1. The lower 5 bits of each character of the prefix. - e.g. "bit..." becomes 2,9,20,...
  2. A zero for the separator (5 zero bits).
  3. The payload by chunks of 5 bits. If necessary, the payload is padded to the right with zero bits to complete any unfinished chunk at the end.
  4. Eight zeros as a "template" for the checksum.

The 40-bit number returned by PolyMod is split into eight 5-bit numbers (msb first). The payload and the checksum are then encoded according to the base32 character table.

To verify a base32-formatted address, it is split at the colon ":" into prefix and payload. Input data (list of integers) for PolyMod function is assembled from these parts:

  1. The lower 5 bits of each characters of the prefix.
  2. A zero for the separator (5 zero bits).
  3. Each base32 char of the payload mapped to it's respective number.

If PolyMod returns non-zero, then the address was broken.

The following adresses can be used as test vector for checksum computation:

  • prefix:x64nx6hz
  • p:gpf8m4h7
  • bitcoincash:qpzry9x8gf2tvdw0s3jn54khce6mua7lcw20ayyn
  • bchtest:testnetaddress4d6njnut
  • bchreg:555555555555555555555555555555555555555555555udxmlmrz

NB: These addresses do not have valid payload on purpose.

Error correction

BCH codes allows for error correction. However, it is strongly advised that error correction is not done in an automatic manner as it may cause funds to be lost irrecoverably if done incorrectly. It may however be used to hint a user at a possible error.

Uppercase/lowercase

Lower case is preferred for cashaddr, but uppercase is accepted. A mixture of lower case and uppercase must be rejected.

Allowing for uppercase ensures that the address can be encoded efficiently in QR codes using the alphanumeric mode[3].

Double prefix

In some contexts, such as payment URLs or QR codes, the addresses are currently prefixed with bitcoincash:. In these contexts, the address must not be double prefixed.

Examples of address translation

The following addresses are given in the legacy and new format.

LegacyCashAddr
1BpEi6DfDAUFd7GtittLSdBeYJvcoaVggubitcoincash:qpm2qsznhks23z7629mms6s4cwef74vcwvy22gdx6a
1KXrWXciRDZUpQwQmuM1DbwsKDLYAYsVLRbitcoincash:qr95sy3j9xwd2ap32xkykttr4cvcu7as4y0qverfuy
16w1D5WRVKJuZUsSRzdLp9w3YGcgoxDXbbitcoincash:qqq3728yw0y47sqn6l2na30mcw6zm78dzqre909m2r
3CWFddi6m4ndiGyKqzYvsFYagqDLPVMTzCbitcoincash:ppm2qsznhks23z7629mms6s4cwef74vcwvn0h829pq
3LDsS579y7sruadqu11beEJoTjdFiFCdX4bitcoincash:pr95sy3j9xwd2ap32xkykttr4cvcu7as4yc93ky28e
31nwvkZwyPdgzjBJZXfDmSWsC4ZLKpYyUwbitcoincash:pqq3728yw0y47sqn6l2na30mcw6zm78dzq5ucqzc37

Larger Test Vectors

This table defines test vectors for various payloads of sizes 160-512 bits with various prefixes. These test vectors aren't given in legacy address format because the legacy format is limited to payloads of 160 bits.

Payload Size (bytes)TypeCashAddrPayload (hex)
200bitcoincash:qr6m7j9njldwwzlg9v7v53unlr4jkmx6eylep8ekg2F5BF48B397DAE70BE82B3CCA4793F8EB2B6CDAC9
201bchtest:pr6m7j9njldwwzlg9v7v53unlr4jkmx6eyvwc0uz5tF5BF48B397DAE70BE82B3CCA4793F8EB2B6CDAC9
201pref:pr6m7j9njldwwzlg9v7v53unlr4jkmx6ey65nvtks5F5BF48B397DAE70BE82B3CCA4793F8EB2B6CDAC9
2015prefix:0r6m7j9njldwwzlg9v7v53unlr4jkmx6ey3qnjwsrfF5BF48B397DAE70BE82B3CCA4793F8EB2B6CDAC9
240bitcoincash:q9adhakpwzztepkpwp5z0dq62m6u5v5xtyj7j3h2ws4mr9g07ADBF6C17084BC86C1706827B41A56F5CA32865925E946EA
241bchtest:p9adhakpwzztepkpwp5z0dq62m6u5v5xtyj7j3h2u94tsynr7ADBF6C17084BC86C1706827B41A56F5CA32865925E946EA
241pref:p9adhakpwzztepkpwp5z0dq62m6u5v5xtyj7j3h2khlwwk5v7ADBF6C17084BC86C1706827B41A56F5CA32865925E946EA
2415prefix:09adhakpwzztepkpwp5z0dq62m6u5v5xtyj7j3h2p29kc2lp7ADBF6C17084BC86C1706827B41A56F5CA32865925E946EA
280bitcoincash:qgagf7w02x4wnz3mkwnchut2vxphjzccwxgjvvjmlsxqwkcw59jxxuz3A84F9CF51AAE98A3BB3A78BF16A6183790B18719126325BFC0C075B
281bchtest:pgagf7w02x4wnz3mkwnchut2vxphjzccwxgjvvjmlsxqwkcvs7md7wt3A84F9CF51AAE98A3BB3A78BF16A6183790B18719126325BFC0C075B
281pref:pgagf7w02x4wnz3mkwnchut2vxphjzccwxgjvvjmlsxqwkcrsr6gzkn3A84F9CF51AAE98A3BB3A78BF16A6183790B18719126325BFC0C075B
2815prefix:0gagf7w02x4wnz3mkwnchut2vxphjzccwxgjvvjmlsxqwkc5djw8s9g3A84F9CF51AAE98A3BB3A78BF16A6183790B18719126325BFC0C075B
320bitcoincash:qvch8mmxy0rtfrlarg7ucrxxfzds5pamg73h7370aa87d80gyhqxq5nlegake3173EF6623C6B48FFD1A3DCC0CC6489B0A07BB47A37F47CFEF4FE69DE825C060
321bchtest:pvch8mmxy0rtfrlarg7ucrxxfzds5pamg73h7370aa87d80gyhqxq7fqng6m63173EF6623C6B48FFD1A3DCC0CC6489B0A07BB47A37F47CFEF4FE69DE825C060
321pref:pvch8mmxy0rtfrlarg7ucrxxfzds5pamg73h7370aa87d80gyhqxq4k9m7qf93173EF6623C6B48FFD1A3DCC0CC6489B0A07BB47A37F47CFEF4FE69DE825C060
3215prefix:0vch8mmxy0rtfrlarg7ucrxxfzds5pamg73h7370aa87d80gyhqxqsh6jgp6w3173EF6623C6B48FFD1A3DCC0CC6489B0A07BB47A37F47CFEF4FE69DE825C060
400bitcoincash:qnq8zwpj8cq05n7pytfmskuk9r4gzzel8qtsvwz79zdskftrzxtar994cgutavfklv39gr3uvzC07138323E00FA4FC122D3B85B9628EA810B3F381706385E289B0B25631197D194B5C238BEB136FB
401bchtest:pnq8zwpj8cq05n7pytfmskuk9r4gzzel8qtsvwz79zdskftrzxtar994cgutavfklvmgm6ynejC07138323E00FA4FC122D3B85B9628EA810B3F381706385E289B0B25631197D194B5C238BEB136FB
401pref:pnq8zwpj8cq05n7pytfmskuk9r4gzzel8qtsvwz79zdskftrzxtar994cgutavfklv0vx5z0w3C07138323E00FA4FC122D3B85B9628EA810B3F381706385E289B0B25631197D194B5C238BEB136FB
4015prefix:0nq8zwpj8cq05n7pytfmskuk9r4gzzel8qtsvwz79zdskftrzxtar994cgutavfklvwsvctzqyC07138323E00FA4FC122D3B85B9628EA810B3F381706385E289B0B25631197D194B5C238BEB136FB
480bitcoincash:qh3krj5607v3qlqh5c3wq3lrw3wnuxw0sp8dv0zugrrt5a3kj6ucysfz8kxwv2k53krr7n933jfsunqex2w82slE361CA9A7F99107C17A622E047E3745D3E19CF804ED63C5C40C6BA763696B98241223D8CE62AD48D863F4CB18C930E4C
481bchtest:ph3krj5607v3qlqh5c3wq3lrw3wnuxw0sp8dv0zugrrt5a3kj6ucysfz8kxwv2k53krr7n933jfsunqnzf7mt6xE361CA9A7F99107C17A622E047E3745D3E19CF804ED63C5C40C6BA763696B98241223D8CE62AD48D863F4CB18C930E4C
481pref:ph3krj5607v3qlqh5c3wq3lrw3wnuxw0sp8dv0zugrrt5a3kj6ucysfz8kxwv2k53krr7n933jfsunqjntdfcwgE361CA9A7F99107C17A622E047E3745D3E19CF804ED63C5C40C6BA763696B98241223D8CE62AD48D863F4CB18C930E4C
4815prefix:0h3krj5607v3qlqh5c3wq3lrw3wnuxw0sp8dv0zugrrt5a3kj6ucysfz8kxwv2k53krr7n933jfsunqakcssnmnE361CA9A7F99107C17A622E047E3745D3E19CF804ED63C5C40C6BA763696B98241223D8CE62AD48D863F4CB18C930E4C
560bitcoincash:qmvl5lzvdm6km38lgga64ek5jhdl7e3aqd9895wu04fvhlnare5937w4ywkq57juxsrhvw8ym5d8qx7sz7zz0zvcypqscw8jd03fD9FA7C4C6EF56DC4FF423BAAE6D495DBFF663D034A72D1DC7D52CBFE7D1E6858F9D523AC0A7A5C34077638E4DD1A701BD017842789982041
561bchtest:pmvl5lzvdm6km38lgga64ek5jhdl7e3aqd9895wu04fvhlnare5937w4ywkq57juxsrhvw8ym5d8qx7sz7zz0zvcypqs6kgdsg2gD9FA7C4C6EF56DC4FF423BAAE6D495DBFF663D034A72D1DC7D52CBFE7D1E6858F9D523AC0A7A5C34077638E4DD1A701BD017842789982041
561pref:pmvl5lzvdm6km38lgga64ek5jhdl7e3aqd9895wu04fvhlnare5937w4ywkq57juxsrhvw8ym5d8qx7sz7zz0zvcypqsammyqfflD9FA7C4C6EF56DC4FF423BAAE6D495DBFF663D034A72D1DC7D52CBFE7D1E6858F9D523AC0A7A5C34077638E4DD1A701BD017842789982041
5615prefix:0mvl5lzvdm6km38lgga64ek5jhdl7e3aqd9895wu04fvhlnare5937w4ywkq57juxsrhvw8ym5d8qx7sz7zz0zvcypqsgjrqpnw8D9FA7C4C6EF56DC4FF423BAAE6D495DBFF663D034A72D1DC7D52CBFE7D1E6858F9D523AC0A7A5C34077638E4DD1A701BD017842789982041
640bitcoincash:qlg0x333p4238k0qrc5ej7rzfw5g8e4a4r6vvzyrcy8j3s5k0en7calvclhw46hudk5flttj6ydvjc0pv3nchp52amk97tqa5zygg96mtky5sv5wD0F346310D5513D9E01E299978624BA883E6BDA8F4C60883C10F28C2967E67EC77ECC7EEEAEAFC6DA89FAD72D11AC961E164678B868AEEEC5F2C1DA08884175B
641bchtest:plg0x333p4238k0qrc5ej7rzfw5g8e4a4r6vvzyrcy8j3s5k0en7calvclhw46hudk5flttj6ydvjc0pv3nchp52amk97tqa5zygg96mc773cwezD0F346310D5513D9E01E299978624BA883E6BDA8F4C60883C10F28C2967E67EC77ECC7EEEAEAFC6DA89FAD72D11AC961E164678B868AEEEC5F2C1DA08884175B
641pref:plg0x333p4238k0qrc5ej7rzfw5g8e4a4r6vvzyrcy8j3s5k0en7calvclhw46hudk5flttj6ydvjc0pv3nchp52amk97tqa5zygg96mg7pj3lh8D0F346310D5513D9E01E299978624BA883E6BDA8F4C60883C10F28C2967E67EC77ECC7EEEAEAFC6DA89FAD72D11AC961E164678B868AEEEC5F2C1DA08884175B
6415prefix:0lg0x333p4238k0qrc5ej7rzfw5g8e4a4r6vvzyrcy8j3s5k0en7calvclhw46hudk5flttj6ydvjc0pv3nchp52amk97tqa5zygg96ms92w6845D0F346310D5513D9E01E299978624BA883E6BDA8F4C60883C10F28C2967E67EC77ECC7EEEAEAFC6DA89FAD72D11AC961E164678B868AEEEC5F2C1DA08884175B

References

[1] https://en.wikipedia.org/wiki/BCH_code

[2] https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki

[3] http://www.thonky.com/qr-code-tutorial/alphanumeric-mode-encoding

Edit this page on GitHub Updated at Sun, May 15, 2022