CompressedPublicKey

33-byte compressed secp256k1 public key

33-byte compressed secp256k1 public key with validated prefix byte.

Overview

CompressedPublicKey is a fixed-size byte type representing a compressed secp256k1 public key. It validates both the length (33 bytes) and the prefix byte (0x02 or 0x03) at construction time.

Definition

class CompressedPublicKey(HexBytes):
    """33-byte compressed secp256k1 public key (0x02 / 0x03 prefix)."""
    _size = 33

Inheritance

• Inherits from HexBytes (from the hexbytes package)

• HexBytes itself inherits from Python's bytes type

• Fully compatible with any API expecting bytes

Construction

CompressedPublicKey can be constructed from:

• Hex strings (with or without "0x" prefix)

• Raw bytes objects

• Integer values

Parameters

Parameter	Type	Required	Description
val	bytes | str | int	Yes	The value to convert to a 33-byte compressed public key

Raises

• ValueError - If the length is not exactly 33 bytes

• ValueError - If the prefix byte is not 0x02 or 0x03

Examples

From Hex String

from seismic_web3 import CompressedPublicKey

# Valid compressed public key (0x02 prefix)
pubkey = CompressedPublicKey(
    "0x02" + "1234567890abcdef" * 4
)

# Valid with 0x03 prefix
pubkey = CompressedPublicKey(
    "0x03" + "fedcba0987654321" * 4
)

From Raw Bytes

from seismic_web3 import CompressedPublicKey

# 33 bytes with valid prefix
raw_bytes = b'\x02' + b'\x12\x34' * 16
pubkey = CompressedPublicKey(raw_bytes)

Derive from Private Key

from eth_keys import keys as eth_keys
from seismic_web3 import PrivateKey, CompressedPublicKey

private_key = PrivateKey(os.urandom(32))
sk = eth_keys.PrivateKey(bytes(private_key))
public_key = CompressedPublicKey(sk.public_key.to_compressed_bytes())

Use in ECDH

from seismic_web3.precompiles import ecdh
from seismic_web3 import CompressedPublicKey, PrivateKey

private_key = PrivateKey(os.urandom(32))
tee_pubkey = CompressedPublicKey(...)  # From w3.seismic.get_tee_public_key()

shared_secret = ecdh(private_key, tee_pubkey)

Validation Errors

from seismic_web3 import CompressedPublicKey

# Wrong length
try:
    invalid = CompressedPublicKey("0x" + "12" * 32)  # 32 bytes, not 33
except ValueError as e:
    print(e)  # "CompressedPublicKey: expected 33 bytes, got 32"

# Invalid prefix
try:
    invalid = CompressedPublicKey("0x01" + "12" * 32)  # Wrong prefix byte
except ValueError as e:
    print(e)  # "Compressed public key must start with 0x02 or 0x03, got 0x01"

Methods

to_0x_hex()

Returns the hex string representation with "0x" prefix.

pubkey = CompressedPublicKey(...)
hex_str = pubkey.to_0x_hex()  # "0x02abcd...ef"

Properties

• Immutable - Cannot be modified after construction

• Hashable - Can be used as dictionary keys or in sets

• 33 bytes - Always exactly 33 bytes

• Valid prefix - Always starts with 0x02 or 0x03

• Compatible with bytes - Passes isinstance(x, bytes) checks

Compressed vs Uncompressed

Seismic uses compressed public keys exclusively:

• Compressed: 33 bytes (1-byte prefix + 32-byte x-coordinate)

• Uncompressed: 65 bytes (1-byte prefix + 32-byte x-coordinate + 32-byte y-coordinate)

The prefix byte indicates the y-coordinate's parity:

• 0x02 - y-coordinate is even

• 0x03 - y-coordinate is odd

Notes

• Used in SeismicElements for encryption_pubkey

• Required for ECDH key derivation in precompiles

• Obtained from w3.seismic.get_tee_public_key() for transaction encryption

• Prefix validation ensures only valid compressed keys are accepted

See Also

• PrivateKey - Corresponding private key type

• Bytes32 - General 32-byte type

• SeismicElements - Uses CompressedPublicKey for encryption

• ecdh - ECDH key derivation with public keys

• get_tee_public_key - Retrieve TEE public key