aws_encryption_sdk.internal.formatting.encryption_context

Components for handling serialization and deserialization of encryption context data in AWS Encryption SDK messages.

Functions

assemble_content_aad(message_id, ...)	Assembles the Body AAD string for a message body structure.
deserialize_encryption_context(...)	Deserializes the contents of a byte string into a dictionary.
read_short(source, offset)	Reads a number from a byte array.
read_string(source, offset, length)	Reads a string from a byte string.
serialize_encryption_context(encryption_context)	Serializes the contents of a dictionary into a byte string.

aws_encryption_sdk.internal.formatting.encryption_context.assemble_content_aad(message_id, aad_content_string, seq_num, length)

Assembles the Body AAD string for a message body structure.

Parameters

• message_id (str) – Message ID

• aad_content_string (aws_encryption_sdk.identifiers.ContentAADString) – ContentAADString object for frame type

• seq_num (int) – Sequence number of frame

• length (int) – Content Length

Returns

Properly formatted AAD bytes for message body structure.

Return type

bytes

Raises

SerializationError – if aad_content_string is not known

aws_encryption_sdk.internal.formatting.encryption_context.serialize_encryption_context(encryption_context)

Serializes the contents of a dictionary into a byte string.

Parameters

encryption_context (dict) – Dictionary of encrytion context keys/values.

Returns

Serialized encryption context

Return type

bytes

aws_encryption_sdk.internal.formatting.encryption_context.read_short(source, offset)

Reads a number from a byte array.

Parameters

• source (bytes) – Source byte string

• offset (int) – Point in byte string to start reading

Returns

Read number and offset at point after read data

Return type

tuple of ints

Raises

SerializationError if unable to unpack

aws_encryption_sdk.internal.formatting.encryption_context.read_string(source, offset, length)

Reads a string from a byte string.

Parameters

• source (bytes) – Source byte string

• offset (int) – Point in byte string to start reading

• length (int) – Length of string to read

Returns

Read string and offset at point after read data

Return type

tuple of str and int

Raises

SerializationError – if unable to unpack

aws_encryption_sdk.internal.formatting.encryption_context.deserialize_encryption_context(serialized_encryption_context)

Deserializes the contents of a byte string into a dictionary.

Parameters

serialized_encryption_context (bytes) – Source byte string containing serialized dictionary

Returns

Deserialized encryption context

Return type

dict

Raises

• SerializationError – if serialized encryption context is too large

• SerializationError – if duplicate key found in serialized encryption context

• SerializationError – if malformed data found in serialized encryption context