Encoding and Decoding

When working with data from an algorand REST server or preparing transactions there is often a need to encode or decode fields.

Encoding Types

JSON

The encoding most often returned when querying the state of the chain is JSON.

It is easy to visually inspect but may be relatively slow to parse.

All byte arrays are base 64 encoded strings

MessagePack

The encoding used when transmitting transactions to a node is MessagePack.

To inspect a given msgpack file contents a convenience commandline tool is provided:

msgpacktool -d < file.msgp

Base64

The encoding for byte arrays is Base64.

This is to make it safe for the byte array to be transmitted as part of a json object.

Base32

The encoding used for Addresses and Transaction Ids is Base32.

Individual Field Encodings

Address

In Algorand a public key is a 32 byte array.

The Address developers or users are typically shown is a 58 character long string corresponding to a base32 encoding of the byte array of the public key + a checksum.

Given an address 4H5UNRBJ2Q6JENAXQ6HNTGKLKINP4J4VTQBEPK5F3I6RDICMZBPGNH6KD4, encoding to and from the public key format can be done as follows:

Python

address = "4H5UNRBJ2Q6JENAXQ6HNTGKLKINP4J4VTQBEPK5F3I6RDICMZBPGNH6KD4"
pk = encoding.decode_address(address)
addr = encoding.encode_address(pk)

assert addr == address

Snippet Source

JavaScript

const address = '4H5UNRBJ2Q6JENAXQ6HNTGKLKINP4J4VTQBEPK5F3I6RDICMZBPGNH6KD4';
const pk = algosdk.decodeAddress(address);
const addr = algosdk.encodeAddress(pk.publicKey);
console.log(address, addr);

Snippet Source

Go

address := "4H5UNRBJ2Q6JENAXQ6HNTGKLKINP4J4VTQBEPK5F3I6RDICMZBPGNH6KD4"
pk, _ := types.DecodeAddress(address)
addr := pk.String()

Snippet Source

Java

String addrAsStr = "4H5UNRBJ2Q6JENAXQ6HNTGKLKINP4J4VTQBEPK5F3I6RDICMZBPGNH6KD4";
// Instantiate a new Address object with string
Address addr = new Address(addrAsStr);
// Or with the bytes
Address addrAgain = new Address(addr.getBytes());
assert addrAgain.equals(addr);

Snippet Source

Byte arrays

When transmitting an array of bytes over the network, byte arrays are base64 encoded. The SDK will handle encoding from a byte array to base64 but may not decode some fields and you’ll have to handle it yourself. For example compiled program results or the keys and values in a state delta in an application call will be returned as base64 encoded strings.

Example:

Given a base64 encoded byte array SGksIEknbSBkZWNvZGVkIGZyb20gYmFzZTY0 it may be decoded as follows:

Python

base64.b64decode(encoded_str).decode("utf-8") print(decoded_str) ``` [Snippet
Source](https://github.com/algorand/js-algorand-sdk/blob/examples/examples/codec.ts#L23-L26)
</TabItem>
<TabItem label='JavaScript' icon='seti:javascript'>
```javascript const b64Encoded = 'SGksIEknbSBkZWNvZGVkIGZyb20gYmFzZTY0'; const b64Decoded =
Buffer.from(b64Encoded, 'base64').toString(); console.log(b64Encoded, b64Decoded); ``` [Snippet
Source](https://github.com/algorand/py-algorand-sdk/blob/examples/examples/codec.py#L24-L27)
</TabItem>
<TabItem label='Go' icon='seti:go'>
```go encoded := "SGksIEknbSBkZWNvZGVkIGZyb20gYmFzZTY0" decoded, _ :=
base64.StdEncoding.DecodeString(encoded) reencoded := base64.StdEncoding.EncodeToString(decoded)
``` [Snippet
Source](https://github.com/algorand/go-algorand-sdk/blob/examples/examples/codec/main.go#L84-L87)
</TabItem>
<TabItem label='Java' icon='seti:java'>
```java String encodedStr = "SGksIEknbSBkZWNvZGVkIGZyb20gYmFzZTY0"; byte[] decodedBytes =
Encoder.decodeFromBase64(encodedStr); String reEncodedStr =
Encoder.encodeToBase64(decodedBytes); assert encodedStr.equals(reEncodedStr); ``` [Snippet
Source](https://github.com/algorand/java-algorand-sdk/blob/examples/examples/src/main/java/com/algorand/examples/CodecExamples.java#L35-L39)
</TabItem>
</Tabs>

### Integers

Integers in algorand are almost always uint64, sometimes it's required to encode them as bytes. For example when passing them as application arguments in an ApplicationCallTransaction. When encoding an integer to pass as an application argument, the integer should be encoded as the big endian 8 byte representation of the integer value.

_Example:_

Given an integer `1337`, you may encode it as:

<Tabs syncKey="lang">
<TabItem label="Python" icon="seti:python">
  ```python
    val = 1337
    encoded_uint = val.to_bytes(8, "big")
    decoded_uint = int.from_bytes(encoded_uint, byteorder="big")
    assert decoded_uint == val

Snippet Source

JavaScript

const int = 1337;
const encoded = algosdk.encodeUint64(int);
const safeDecoded = algosdk.decodeUint64(encoded, 'safe');
const mixedDecoded = algosdk.decodeUint64(encoded, 'bigint');
console.log(int, encoded, safeDecoded, mixedDecoded);

Snippet Source

Go

val := 1337
encodedInt := make([]byte, 8)
binary.BigEndian.PutUint64(encodedInt, uint64(val))

decodedInt := binary.BigEndian.Uint64(encodedInt)
// decodedInt == val

Snippet Source

Java

BigInteger val = BigInteger.valueOf(1337);
byte[] encodedVal = Encoder.encodeUint64(val);
BigInteger decodedVal = Encoder.decodeUint64(encodedVal);
assert val.equals(decodedVal);

Snippet Source

Working with Encoded Structures

transactions

Sometimes an application needs to transmit a transaction or transaction group between the front end and back end. This can be done by msgpack encoding the transaction object on one side and msgpack decoding it on the other side. Often the msgpack’d bytes will be base64 encoded so that they can be safely transmitted in some json payload so we use that encoding here.

Essentially the encoding is:

tx_byte_str = base64encode(msgpack_encode(tx_obj))

and decoding is:

tx_obj = msgpack_decode(base64decode(tx_byte_str))

Example:

Create a payment transaction from one account to another using suggested parameters and amount 10000, we write the msgpack encoded bytes