| CIP | Title | Status | Category | Authors | Implementors | Discussions | Type | Created | License | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
16 |
Cryptographic Key Serialisation Formats |
Active |
Tools |
|
|
Standards |
2020-12-21 |
Apache-2.0 |
This CIP defines serialisation formats for the following types of cryptographic keys across the Cardano eco-system:
-
Regular Ed25519 keys
-
BIP32-Ed25519 extended keys (Ed25519 extended keys with BIP32-style derivation)
Throughout the Cardano eco-system, different projects have used different serialisation formats for cryptographic keys.
For example, for BIP32-Ed25519 extended signing keys, the
cardano-crypto
implementation supports a 128-byte binary serialization format, while
jcli
and
cardano-addresses
supports a 96-byte binary serialization format.
Another example would be
cardano-cli which
supports a custom JSON format, referred to as "text envelope", (which can be
used for serialising keys) that isn't supported by other projects in the
eco-system.
This has introduced compatibility problems for both users and developers:
-
Users cannot easily utilize their keys across different tools and software in the Cardano eco-system as they may be serialized in different ways.
-
Developers wanting to support the different serialisation formats may need to write potentially error-prone (de)serialisation and conversion operations.
Therefore, this CIP aims to define standard cryptographic key serialisation formats to be used by projects throughout the Cardano eco-system.
For the verification (public) key binary format, we simply use the raw 32-byte Ed25519 public key data.
This structure should be Bech32 encoded, using one of the appropriate *_vk
prefixes defined in CIP-0005.
For extended verification (public) keys, we define the following 64-byte binary format:
+-----------------------+-----------------------+
| Public Key (32 bytes) | Chain Code (32 bytes) |
+-----------------------+-----------------------+
That is, a 32-byte Ed25519 public key followed by a 32-byte chain code.
This structure should be Bech32 encoded, using one of the appropriate *_xvk
prefixes defined in CIP-0005.
For the signing (private) key binary format, we simply use the raw 32-byte Ed25519 private key data.
This structure should be Bech32 encoded, using one of the appropriate *_sk
prefixes defined in CIP-0005.
For extended signing (private) keys, we define the following 96-byte binary format:
+---------------------------------+-----------------------+
| Extended Private Key (64 bytes) | Chain Code (32 bytes) |
+---------------------------------+-----------------------+
That is, a 64-byte Ed25519 extended private key followed by a 32-byte chain code.
This structure should be Bech32 encoded, using one of the appropriate *_xsk
prefixes defined in CIP-0005.
As mentioned in the Abstract, the original
cardano-crypto
implementation defined a 128-byte binary serialization format for
BIP32-Ed25519 extended signing keys:
+---------------------------------+-----------------------+-----------------------+
| Extended Private Key (64 bytes) | Public Key (32 bytes) | Chain Code (32 bytes) |
+---------------------------------+-----------------------+-----------------------+
However, as it turns out, keeping around the 32-byte Ed25519 public key is redundant as it can easily be derived from the Ed25519 private key (the first 32 bytes of the 64-byte extended private key).
Therefore, because other projects such as
jcli
and
cardano-addresses
already utilize the more compact 96-byte format, we opt to define that as the
standard.
- Confirm support by applications and tools from different developers:
N/A
This CIP is licensed under Apache-2.0.