zeth.core.encryption Namespace Reference

Classes
class	EncryptionKeyPair

Functions
EncryptionSecretKey	generate_encryption_secret_key ()
bytes	encode_encryption_secret_key (EncryptionSecretKey sk)
EncryptionSecretKey	decode_encryption_secret_key (bytes sk_bytes)
str	encryption_secret_key_as_hex (EncryptionSecretKey sk)
EncryptionSecretKey	encryption_secret_key_from_hex (str pk_str)
EncryptionPublicKey	get_encryption_public_key (EncryptionSecretKey enc_secret)
bytes	encode_encryption_public_key (EncryptionPublicKey pk)
EncryptionPublicKey	decode_encryption_public_key (bytes pk_data)
str	encryption_public_key_as_hex (EncryptionPublicKey pk)
EncryptionPublicKey	encryption_public_key_from_hex (str pk_str)
EncryptionKeyPair	generate_encryption_keypair ()
bytes	encrypt (bytes message, EncryptionPublicKey pk_receiver)
bytes	decrypt (bytes encrypted_message, EncryptionSecretKey sk_receiver)

Variables
	int
	bytes
	InvalidSignature = cryptography_InvalidSignature
	EncryptionSecretKey = NewType('EncryptionSecretKey', object)
	EncryptionPublicKey = NewType('EncryptionPublicKey', object)

Function Documentation

decode_encryption_public_key()

EncryptionPublicKey zeth.core.encryption.decode_encryption_public_key

(

bytes

pk_data

)

Definition at line 142 of file encryption.py.

def decode_encryption_public_key(pk_data: bytes) -> EncryptionPublicKey:
    return EncryptionPublicKey(X25519PublicKey.from_public_bytes(pk_data))
 
 

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decode_encryption_secret_key()

EncryptionSecretKey zeth.core.encryption.decode_encryption_secret_key

(

bytes

sk_bytes

)

Definition at line 115 of file encryption.py.

def decode_encryption_secret_key(sk_bytes: bytes) -> EncryptionSecretKey:
    return EncryptionSecretKey(
        X25519PrivateKey.from_private_bytes(sk_bytes))
 
 

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decrypt()

bytes zeth.core.encryption.decrypt	(	bytes	encrypted_message,
		EncryptionSecretKey	sk_receiver
	)

Decrypts a NOTE_LENGTH-byte message by using valid ec25519 private key
objects.  See: https://pynacl.readthedocs.io/en/stable/public/

Definition at line 203 of file encryption.py.

def decrypt(
        encrypted_message: bytes,
        sk_receiver: EncryptionSecretKey) -> bytes:
    """
    Decrypts a NOTE_LENGTH-byte message by using valid ec25519 private key
    objects.  See: https://pynacl.readthedocs.io/en/stable/public/
    """
    assert \
        len(encrypted_message) == ENCRYPTED_NOTE_LENGTH_BYTES, \
        "encrypted_message byte-length must be: "+str(ENCRYPTED_NOTE_LENGTH_BYTES)
 
    assert(isinstance(sk_receiver, X25519PrivateKey)), \
        f"PrivateKey: {sk_receiver} ({type(sk_receiver)})"
 
    # Compute shared secret
    pk_sender_bytes = encrypted_message[:EC_PUBLIC_KEY_LENGTH_BYTES]
    pk_sender = decode_encryption_public_key(pk_sender_bytes)
    shared_key = _exchange(sk_receiver, pk_sender)
 
    # Generate key material and recover keys
    sym_key, mac_key = _kdf(pk_sender_bytes, shared_key)
 
    # ct_sym and mac
    ct_sym = encrypted_message[
        EC_PUBLIC_KEY_LENGTH_BYTES:
        EC_PUBLIC_KEY_LENGTH_BYTES + NOTE_LENGTH_BYTES]
    tag = encrypted_message[
        EC_PUBLIC_KEY_LENGTH_BYTES + NOTE_LENGTH_BYTES:
        EC_PUBLIC_KEY_LENGTH_BYTES + NOTE_LENGTH_BYTES + _TAG_LENGTH_BYTES]
 
    # Verify the mac
    mac = poly1305.Poly1305(mac_key)
    mac.update(ct_sym)
    mac.verify(tag)
 
    # Decrypt sym ciphertext
    algorithm = algorithms.ChaCha20(sym_key, _SYM_NONCE_VALUE)
    cipher = Cipher(algorithm, mode=None, backend=default_backend())
    decryptor = cipher.decryptor()
    message = decryptor.update(ct_sym)
 
    return message
 
 

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encode_encryption_public_key()

bytes zeth.core.encryption.encode_encryption_public_key

(

EncryptionPublicKey

pk

)

Definition at line 138 of file encryption.py.

def encode_encryption_public_key(pk: EncryptionPublicKey) -> bytes:
    return pk.public_bytes(Encoding.Raw, PublicFormat.Raw)  # type: ignore
 
 

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encode_encryption_secret_key()

bytes zeth.core.encryption.encode_encryption_secret_key

(

EncryptionSecretKey

sk

)

Definition at line 110 of file encryption.py.

def encode_encryption_secret_key(sk: EncryptionSecretKey) -> bytes:
    return sk.private_bytes(  # type: ignore
        Encoding.Raw, PrivateFormat.Raw, NoEncryption())
 
 

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encrypt()

bytes zeth.core.encryption.encrypt	(	bytes	message,
		EncryptionPublicKey	pk_receiver
	)

Encrypts a string message under a ec25519 public key by using a custom
dhaes-based scheme.  See: https://eprint.iacr.org/1999/007

Definition at line 168 of file encryption.py.

def encrypt(message: bytes, pk_receiver: EncryptionPublicKey) -> bytes:
    """
    Encrypts a string message under a ec25519 public key by using a custom
    dhaes-based scheme.  See: https://eprint.iacr.org/1999/007
    """
    assert \
        len(message) == NOTE_LENGTH_BYTES, \
        f"expected message length {NOTE_LENGTH_BYTES}, saw {len(message)}"
 
    # Generate ephemeral keypair
    eph_keypair = generate_encryption_keypair()
 
    # Compute shared secret and eph key
    shared_key = _exchange(eph_keypair.k_sk, pk_receiver)
    pk_sender_bytes = encode_encryption_public_key(eph_keypair.k_pk)
 
    # Generate key material
    sym_key, mac_key = _kdf(pk_sender_bytes, shared_key)
 
    # Generate symmetric ciphertext
    # Chacha encryption
    algorithm = algorithms.ChaCha20(sym_key, _SYM_NONCE_VALUE)
    cipher = Cipher(algorithm, mode=None, backend=default_backend())
    encryptor = cipher.encryptor()
    sym_ciphertext = encryptor.update(message)
 
    # Generate mac
    mac = poly1305.Poly1305(mac_key)
    mac.update(sym_ciphertext)
    tag = mac.finalize()
 
    # Arrange ciphertext
    return pk_sender_bytes+sym_ciphertext+tag
 
 

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encryption_public_key_as_hex()

str zeth.core.encryption.encryption_public_key_as_hex

(

EncryptionPublicKey

pk

)

Definition at line 146 of file encryption.py.

def encryption_public_key_as_hex(pk: EncryptionPublicKey) -> str:
    return encode_encryption_public_key(pk).hex()
 
 

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encryption_public_key_from_hex()

EncryptionPublicKey zeth.core.encryption.encryption_public_key_from_hex

(

str

pk_str

)

Definition at line 150 of file encryption.py.

def encryption_public_key_from_hex(pk_str: str) -> EncryptionPublicKey:
    return decode_encryption_public_key(bytes.fromhex(pk_str))
 
 

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encryption_secret_key_as_hex()

str zeth.core.encryption.encryption_secret_key_as_hex

(

EncryptionSecretKey

sk

)

Definition at line 120 of file encryption.py.

def encryption_secret_key_as_hex(sk: EncryptionSecretKey) -> str:
    return encode_encryption_secret_key(sk).hex()  # type: ignore
 
 

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encryption_secret_key_from_hex()

EncryptionSecretKey zeth.core.encryption.encryption_secret_key_from_hex

(

str

pk_str

)

Definition at line 124 of file encryption.py.

def encryption_secret_key_from_hex(pk_str: str) -> EncryptionSecretKey:
    return EncryptionSecretKey(
        X25519PrivateKey.from_private_bytes(bytes.fromhex(pk_str)))
 
 
# Public key for decryption

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generate_encryption_keypair()

EncryptionKeyPair zeth.core.encryption.generate_encryption_keypair

(

)

Definition at line 163 of file encryption.py.

def generate_encryption_keypair() -> EncryptionKeyPair:
    sk = generate_encryption_secret_key()
    return EncryptionKeyPair(sk, get_encryption_public_key(sk))
 
 

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generate_encryption_secret_key()

EncryptionSecretKey zeth.core.encryption.generate_encryption_secret_key

(

)

Definition at line 106 of file encryption.py.

def generate_encryption_secret_key() -> EncryptionSecretKey:
    return EncryptionSecretKey(X25519PrivateKey.generate())  # type: ignore
 
 

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get_encryption_public_key()

EncryptionPublicKey zeth.core.encryption.get_encryption_public_key

(

EncryptionSecretKey

enc_secret

)

Definition at line 133 of file encryption.py.

def get_encryption_public_key(
        enc_secret: EncryptionSecretKey) -> EncryptionPublicKey:
    return enc_secret.public_key()  # type: ignore
 
 

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Variable Documentation

bytes

zeth.core.encryption.bytes

Definition at line 87 of file encryption.py.

EncryptionPublicKey

zeth.core.encryption.EncryptionPublicKey = NewType('EncryptionPublicKey', object)

Definition at line 130 of file encryption.py.

EncryptionSecretKey

zeth.core.encryption.EncryptionSecretKey = NewType('EncryptionSecretKey', object)

Definition at line 103 of file encryption.py.

int

zeth.core.encryption.int

Definition at line 72 of file encryption.py.

InvalidSignature

zeth.core.encryption.InvalidSignature = cryptography_InvalidSignature

Definition at line 100 of file encryption.py.