def try_rehom(rhs: Expression, expected_type: AnnotatedTypeName):
if rhs.annotated_type.is_public():
raise ValueError(
'Cannot change the homomorphism of a public value')
if rhs.annotated_type.is_private_at_me(rhs.analysis):
# The value is @me, so we can just insert a ReclassifyExpr to change
# the homomorphism of this value, just like we do for public values.
return TypeCheckVisitor.make_rehom(rhs, expected_type)
if isinstance(rhs, ReclassifyExpr) and not isinstance(rhs, RehomExpr):
# rhs is a valid ReclassifyExpr, i.e. the argument is public or @me-private
# To create an expression with the correct homomorphism,
# just change the ReclassifyExpr's output homomorphism
rhs.homomorphism = expected_type.homomorphism
elif isinstance(rhs, PrimitiveCastExpr):
# Ignore primitive cast & recurse
rhs.expr = TypeCheckVisitor.try_rehom(rhs.expr, expected_type)
elif isinstance(rhs, FunctionCallExpr) and isinstance(rhs.func, BuiltinFunction) and rhs.func.is_ite() \
and rhs.args[0].annotated_type.is_public():
# Argument is public_cond ? true_val : false_val. Try to rehom both true_val and false_val
rhs.args[1] = TypeCheckVisitor.try_rehom(rhs.args[1],
expected_type)
rhs.args[2] = TypeCheckVisitor.try_rehom(rhs.args[2],
expected_type)
else:
raise TypeMismatchException(expected_type, rhs.annotated_type, rhs)
# Rehom worked without throwing, change annotated_type and return
rhs.annotated_type = rhs.annotated_type.with_homomorphism(
expected_type.homomorphism)
return rhs
def make_private_if_not_already(self, ast: Expression):
if ast.annotated_type.is_private():
expected = AnnotatedTypeName(ast.annotated_type.type_name,
Expression.me_expr())
if not ast.instanceof(expected):
raise TypeMismatchException(expected, ast.annotated_type, ast)
return ast
else:
return self.make_private(ast, Expression.me_expr())
def handle_cast(self, expr: Expression, t: TypeName) -> AnnotatedTypeName:
# because of the fake solidity check we already know that the cast is possible -> don't have to check if cast possible
if expr.annotated_type.is_private():
expected = AnnotatedTypeName(expr.annotated_type.type_name,
Expression.me_expr())
if not expr.instanceof(expected):
raise TypeMismatchException(expected, expr.annotated_type,
expr)
return AnnotatedTypeName(t.clone(), Expression.me_expr())
else:
return AnnotatedTypeName(t.clone())
def assign_location(target: Expression, source: Expression):
# set statement
target.statement = source.statement
# set parents
target.parent = source.parent
target.annotated_type.parent = target
source.parent = target
# set source location
target.line = source.line
target.column = source.column
def _ensure_encryption(self, stmt: Statement, plain: HybridArgumentIdf,
new_privacy: PrivacyLabelExpr,
crypto_params: CryptoParams,
cipher: HybridArgumentIdf, is_param: bool,
is_dec: bool):
"""
Make sure that cipher = enc(plain, getPk(new_privacy), priv_user_provided_rnd).
This automatically requests necessary keys and adds a circuit input for the randomness.
Note: This function adds pre-statements to stmt
:param stmt [SIDE EFFECT]: the statement which contains the expression which requires this encryption
:param plain: circuit variable referencing the plaintext value
:param new_privacy: privacy label corresponding to the destination key address
:param cipher: circuit variable referencing the encrypted value
:param is_param: whether cipher is a function parameter
:param is_dec: whether this is a decryption operation (user supplied plain) as opposed to an encryption operation (user supplied cipher)
"""
if crypto_params.is_symmetric_cipher():
# Need a different set of keys for hybrid-encryption (ecdh-based) backends
self._require_secret_key(crypto_params)
my_pk = self._require_public_key_for_label_at(
stmt, Expression.me_expr(), crypto_params)
if is_dec:
other_pk = self._get_public_key_in_sender_field(
stmt, cipher, crypto_params)
else:
if new_privacy == Expression.me_expr():
other_pk = my_pk
else:
other_pk = self._require_public_key_for_label_at(
stmt, new_privacy, crypto_params)
self.phi.append(
CircComment(
f'{cipher.name} = enc({plain.name}, ecdh({other_pk.name}, my_sk))'
))
self._phi.append(
CircSymmEncConstraint(plain, other_pk, cipher, is_dec))
else:
rnd = self._secret_input_name_factory.add_idf(
f'{plain.name if is_param else cipher.name}_R',
TypeName.rnd_type(crypto_params))
pk = self._require_public_key_for_label_at(stmt, new_privacy,
crypto_params)
if not is_dec:
self.phi.append(
CircComment(
f'{cipher.name} = enc({plain.name}, {pk.name})'))
self._phi.append(CircEncConstraint(plain, rnd, pk, cipher, is_dec))
def make_private(expr: Expression, privacy: Expression,
homomorphism: Homomorphism):
assert (privacy.privacy_annotation_label() is not None)
pl = get_privacy_expr_from_label(privacy.privacy_annotation_label())
r = ReclassifyExpr(expr, pl, homomorphism)
# set type
r.annotated_type = AnnotatedTypeName(expr.annotated_type.type_name,
pl.clone(), homomorphism)
TypeCheckVisitor.check_for_invalid_private_type(r)
# set statement, parents, location
TypeCheckVisitor.assign_location(r, expr)
return r
def get_rhs(self, rhs: Expression, expected_type: AnnotatedTypeName):
if isinstance(rhs, TupleExpr):
if not isinstance(rhs, TupleExpr) or not isinstance(
expected_type.type_name, TupleType) or len(
rhs.elements) != len(expected_type.type_name.types):
raise TypeMismatchException(expected_type, rhs.annotated_type,
rhs)
exprs = [
self.get_rhs(a, e)
for e, a, in zip(expected_type.type_name.types, rhs.elements)
]
return replace_expr(rhs, TupleExpr(exprs)).as_type(
TupleType([e.annotated_type for e in exprs]))
instance = rhs.instanceof(expected_type)
if not instance:
raise TypeMismatchException(expected_type, rhs.annotated_type, rhs)
else:
if rhs.annotated_type.type_name != expected_type.type_name:
rhs = self.implicitly_converted_to(rhs,
expected_type.type_name)
if instance == 'make-private':
return self.make_private(rhs, expected_type.privacy_annotation)
else:
return rhs
def visitAnnotatedTypeName(self, ast: AnnotatedTypeName):
if type(ast.type_name) == UserDefinedTypeName:
if not isinstance(ast.type_name.target, EnumDefinition):
raise TypeException('Unsupported use of user-defined type',
ast.type_name)
ast.type_name = ast.type_name.target.annotated_type.type_name.clone(
)
if ast.privacy_annotation != Expression.all_expr():
if not ast.type_name.can_be_private():
raise TypeException(
f'Currently, we do not support private {str(ast.type_name)}',
ast)
p = ast.privacy_annotation
if isinstance(p, IdentifierExpr):
t = p.target
if isinstance(t, Mapping):
# no action necessary, this is the case: mapping(address!x => uint@x)
pass
elif not t.is_final and not t.is_constant:
raise TypeException(
'Privacy annotations must be "final" or "constant", if they are expressions',
p)
elif t.annotated_type != AnnotatedTypeName.address_all():
raise TypeException(
f'Privacy type is not a public address, but {str(t.annotated_type)}',
p)
def visitIfStatement(self, ast: IfStatement):
b = ast.condition
if not b.instanceof_data_type(TypeName.bool_type()):
raise TypeMismatchException(TypeName.bool_type(),
b.annotated_type.type_name, b)
if ast.condition.annotated_type.is_private():
expected = AnnotatedTypeName(TypeName.bool_type(),
Expression.me_expr())
if not b.instanceof(expected):
raise TypeMismatchException(expected, b.annotated_type, b)
def implicitly_converted_to(expr: Expression, t: TypeName) -> Expression:
if isinstance(expr, ReclassifyExpr) and not expr.privacy.is_all_expr():
# Cast the argument of the ReclassifyExpr instead
expr.expr = TypeCheckVisitor.implicitly_converted_to(expr.expr, t)
expr.annotated_type.type_name = expr.expr.annotated_type.type_name
return expr
assert expr.annotated_type.type_name.is_primitive_type()
cast = PrimitiveCastExpr(t.clone(), expr, is_implicit=True).override(
parent=expr.parent,
statement=expr.statement,
line=expr.line,
column=expr.column)
cast.elem_type.parent = cast
expr.parent = cast
cast.annotated_type = AnnotatedTypeName(
t.clone(), expr.annotated_type.privacy_annotation.clone(),
expr.annotated_type.homomorphism).override(parent=cast)
return cast
def replace_expr(old_expr: Expression,
new_expr: Expression,
copy_type: bool = False):
"""
Copies over ast common ast attributes and reruns, parent setter, symbol table, side effect detector
"""
_replace_ast(old_expr, new_expr)
if copy_type:
new_expr.annotated_type = old_expr.annotated_type
return new_expr
def implicitly_converted_to(expr: Expression, t: TypeName) -> Expression:
assert expr.annotated_type.type_name.is_primitive_type()
cast = PrimitiveCastExpr(t.clone(), expr, is_implicit=True).override(
parent=expr.parent,
statement=expr.statement,
line=expr.line,
column=expr.column)
cast.elem_type.parent = cast
expr.parent = cast
cast.annotated_type = AnnotatedTypeName(
t.clone(),
expr.annotated_type.privacy_annotation.clone()).override(
parent=cast)
return cast
def make_private(expr: Expression, privacy: Expression):
assert (privacy.privacy_annotation_label() is not None)
pl = get_privacy_expr_from_label(privacy.privacy_annotation_label())
r = ReclassifyExpr(expr, pl)
# set type
r.annotated_type = AnnotatedTypeName(expr.annotated_type.type_name,
pl.clone())
TypeCheckVisitor.check_for_invalid_private_type(r)
# set statement
r.statement = expr.statement
# set parents
r.parent = expr.parent
r.annotated_type.parent = r
expr.parent = r
# set source location
r.line = expr.line
r.column = expr.column
return r
def ensure_parameter_encryption(self, insert_loc_stmt: Statement,
param: Parameter):
"""
Make circuit prove that the encryption of the specified parameter is correct.
"""
assert param.annotated_type.is_cipher()
plain_idf = self._secret_input_name_factory.add_idf(
param.idf.name, param.annotated_type.zkay_type.type_name)
name = f'{self._in_name_factory.get_new_name(param.annotated_type.type_name)}_{param.idf.name}'
cipher_idf = self._in_name_factory.add_idf(
name, param.annotated_type.type_name)
self._ensure_encryption(insert_loc_stmt, plain_idf,
Expression.me_expr(),
param.annotated_type.type_name.crypto_params,
cipher_idf, True, False)
def evaluate_expr_in_circuit(self, expr: Expression,
new_privacy: PrivacyLabelExpr,
homomorphism: Homomorphism) -> LocationExpr:
"""
Evaluate private expression and return result as a fresh out variable.
Roughly corresponds to out() from paper
Note: This function has side effects on expr.statement (adds a pre_statement)
:param expr: [SIDE EFFECT] The expression which should be evaluated privately
:param new_privacy: The circuit output should be encrypted for this owner (or plain if 'all')
:return: Location expression which references the encrypted circuit result
"""
with self.circ_indent_block(expr.code()):
return self._get_circuit_output_for_private_expression(
expr, new_privacy, homomorphism)
def visitAnnotatedTypeName(self, ast: AnnotatedTypeName):
if type(ast.type_name) == UserDefinedTypeName:
if not isinstance(ast.type_name.target, EnumDefinition):
raise TypeException('Unsupported use of user-defined type',
ast.type_name)
ast.type_name = ast.type_name.target.annotated_type.type_name.clone(
)
if ast.privacy_annotation != Expression.all_expr():
if not ast.type_name.can_be_private():
raise TypeException(
f'Currently, we do not support private {str(ast.type_name)}',
ast)
if ast.homomorphism != Homomorphism.NON_HOMOMORPHIC:
# only support uint8, uint16, uint24, uint32 homomorphic data types
if not ast.type_name.is_numeric:
raise TypeException(
f'Homomorphic type not supported for {str(ast.type_name)}: Only numeric types supported',
ast)
elif ast.type_name.signed:
raise TypeException(
f'Homomorphic type not supported for {str(ast.type_name)}: Only unsigned types supported',
ast)
elif ast.type_name.elem_bitwidth > 32:
raise TypeException(
f'Homomorphic type not supported for {str(ast.type_name)}: Only up to 32-bit numeric types supported',
ast)
p = ast.privacy_annotation
if isinstance(p, IdentifierExpr):
t = p.target
if isinstance(t, Mapping):
# no action necessary, this is the case: mapping(address!x => uint@x)
pass
elif not t.is_final and not t.is_constant:
raise TypeException(
'Privacy annotations must be "final" or "constant", if they are expressions',
p)
elif t.annotated_type != AnnotatedTypeName.address_all():
raise TypeException(
f'Privacy type is not a public address, but {str(t.annotated_type)}',
p)
def visitReclassifyExpr(self, ast: ReclassifyExpr):
if self.inside_privif_stmt and not ast.statement.before_analysis.same_partition(
ast.privacy.privacy_annotation_label(), Expression.me_expr()):
raise TypeException(
'Revealing information to other parties is not allowed inside private if statements',
ast)
if ast.expr.annotated_type.is_public():
eval_in_public = False
try:
self.priv_setter.set_evaluation(ast, evaluate_privately=True)
except TypeException:
eval_in_public = True
if eval_in_public or not self.should_evaluate_public_expr_in_circuit(
ast.expr):
self.priv_setter.set_evaluation(ast.expr,
evaluate_privately=False)
else:
self.priv_setter.set_evaluation(ast, evaluate_privately=True)
self.visit(ast.expr)
def visitIndexExpr(self, ast: IndexExpr):
arr = ast.arr
index = ast.key
map_t = arr.annotated_type
# should have already been checked
assert (map_t.privacy_annotation.is_all_expr())
# do actual type checking
if isinstance(map_t.type_name, Mapping):
key_type = map_t.type_name.key_type
expected = AnnotatedTypeName(key_type, Expression.all_expr())
instance = index.instanceof(expected)
if not instance:
raise TypeMismatchException(expected, index.annotated_type,
ast)
# record indexing information
if map_t.type_name.key_label is not None: # TODO modification correct?
if index.privacy_annotation_label():
map_t.type_name.instantiated_key = index
else:
raise TypeException(
f'Index cannot be used as a privacy type for array of type {map_t}',
ast)
# determine value type
ast.annotated_type = map_t.type_name.value_type
if not self.is_accessible_by_invoker(ast):
raise TypeException(
"Tried to read value which cannot be proven to be owned by the transaction invoker",
ast)
elif isinstance(map_t.type_name, Array):
if ast.key.annotated_type.is_private():
raise TypeException('No private array index', ast)
if not ast.key.instanceof_data_type(TypeName.number_type()):
raise TypeException('Array index must be numeric', ast)
ast.annotated_type = map_t.type_name.value_type
else:
raise TypeException('Indexing into non-mapping', ast)
def visitIfStatement(self, ast: IfStatement):
old_in_privif_stmt = self.inside_privif_stmt
if ast.condition.annotated_type.is_private():
mod_vals = set(ast.then_branch.modified_values.keys())
if ast.else_branch is not None:
mod_vals = mod_vals.union(ast.else_branch.modified_values)
for val in mod_vals:
if not val.target.annotated_type.zkay_type.type_name.is_primitive_type(
):
raise TypeException(
'Writes to non-primitive type variables are not allowed inside private if statements',
ast)
if val.in_scope_at(
ast) and not ast.before_analysis.same_partition(
val.privacy, Expression.me_expr()):
raise TypeException(
'If statement with private condition must not contain side effects to variables with owner != me',
ast)
self.inside_privif_stmt = True
self.priv_setter.set_evaluation(ast, evaluate_privately=True)
self.visitChildren(ast)
self.inside_privif_stmt = old_in_privif_stmt
def create_external_wrapper_body(int_fct: ConstructorOrFunctionDefinition,
ext_circuit: CircuitHelper,
original_params: List[Parameter],
requires_proof: bool) -> Block:
"""
Return Block with external wrapper function body.
:param int_fct: corresponding internal function
:param ext_circuit: [SIDE EFFECT] circuit helper of the external wrapper function
:param original_params: list of transformed function parameters without additional parameters added due to transformation
:return: body with wrapper code
"""
has_priv_args = any(
[p.annotated_type.is_cipher() for p in original_params])
stmts = []
if has_priv_args:
ext_circuit._require_public_key_for_label_at(
None, Expression.me_expr())
if cfg.is_symmetric_cipher():
# Make sure msg.sender's key pair is available in the circuit
assert any(isinstance(k, MeExpr) for k in ext_circuit.requested_global_keys) \
or has_priv_args, "requires verification => both sender keys required"
stmts += ext_circuit.request_private_key()
# Verify that out parameter has correct size
stmts += [
RequireStatement(
IdentifierExpr(cfg.zk_out_name).dot('length').binop(
'==', NumberLiteralExpr(ext_circuit.out_size_trans)))
]
# IdentifierExpr for array var holding serialized public circuit inputs
in_arr_var = IdentifierExpr(cfg.zk_in_name).as_type(
Array(AnnotatedTypeName.uint_all()))
# Find index of me's public key in requested_global_keys
glob_me_key_index = -1
for idx, e in enumerate(ext_circuit.requested_global_keys):
if isinstance(e, MeExpr):
glob_me_key_index = idx
break
# Request static public keys
offset = 0
key_req_stmts = []
if ext_circuit.requested_global_keys:
# Ensure that me public key is stored starting at in[0]
keys = [key for key in ext_circuit.requested_global_keys]
if glob_me_key_index != -1:
(keys[0], keys[glob_me_key_index]) = (keys[glob_me_key_index],
keys[0])
tmp_key_var = Identifier('_tmp_key')
key_req_stmts.append(
tmp_key_var.decl_var(AnnotatedTypeName.key_type()))
for key_owner in keys:
idf, assignment = ext_circuit.request_public_key(
key_owner, ext_circuit.get_glob_key_name(key_owner))
assignment.lhs = IdentifierExpr(tmp_key_var.clone())
key_req_stmts.append(assignment)
# Manually add to circuit inputs
key_req_stmts.append(
in_arr_var.slice(offset, cfg.key_len).assign(
IdentifierExpr(tmp_key_var.clone()).slice(
0, cfg.key_len)))
offset += cfg.key_len
assert offset == ext_circuit.in_size
# Check encrypted parameters
param_stmts = []
for p in original_params:
""" * of T_e rule 8 """
if p.annotated_type.is_cipher():
assign_stmt = in_arr_var.slice(
offset, cfg.cipher_payload_len).assign(
IdentifierExpr(p.idf.clone()).slice(
0, cfg.cipher_payload_len))
ext_circuit.ensure_parameter_encryption(assign_stmt, p)
# Manually add to circuit inputs
param_stmts.append(assign_stmt)
offset += cfg.cipher_payload_len
if cfg.is_symmetric_cipher():
# Populate sender field of encrypted parameters
copy_stmts = []
for p in original_params:
if p.annotated_type.is_cipher():
sender_key = in_arr_var.index(0)
idf = IdentifierExpr(p.idf.clone()).as_type(
p.annotated_type.clone())
lit = ArrayLiteralExpr([
idf.clone().index(i)
for i in range(cfg.cipher_payload_len)
] + [sender_key])
copy_stmts.append(
VariableDeclarationStatement(
VariableDeclaration([], p.annotated_type.clone(),
p.idf.clone(), 'memory'), lit))
if copy_stmts:
param_stmts += [
Comment(),
Comment(
'Copy from calldata to memory and set sender field')
] + copy_stmts
assert glob_me_key_index != -1, "Symmetric cipher but did not request me key"
# Declare in array
new_in_array_expr = NewExpr(
AnnotatedTypeName(TypeName.dyn_uint_array()),
[NumberLiteralExpr(ext_circuit.in_size_trans)])
in_var_decl = in_arr_var.idf.decl_var(TypeName.dyn_uint_array(),
new_in_array_expr)
stmts.append(in_var_decl)
stmts.append(Comment())
stmts += Comment.comment_wrap_block('Request static public keys',
key_req_stmts)
stmts += Comment.comment_wrap_block(
'Backup private arguments for verification', param_stmts)
# Call internal function
args = [IdentifierExpr(param.idf.clone()) for param in original_params]
internal_call = FunctionCallExpr(
IdentifierExpr(int_fct.idf.clone()).override(target=int_fct), args)
internal_call.sec_start_offset = ext_circuit.priv_in_size
if int_fct.requires_verification:
ext_circuit.call_function(internal_call)
args += [
in_arr_var.clone(),
NumberLiteralExpr(ext_circuit.in_size),
IdentifierExpr(cfg.zk_out_name),
NumberLiteralExpr(ext_circuit.out_size)
]
if int_fct.return_parameters:
stmts += Comment.comment_list("Declare return variables", [
VariableDeclarationStatement(deep_copy(vd))
for vd in int_fct.return_var_decls
])
in_call = TupleExpr([
IdentifierExpr(vd.idf.clone())
for vd in int_fct.return_var_decls
]).assign(internal_call)
else:
in_call = ExpressionStatement(internal_call)
stmts.append(Comment("Call internal function"))
stmts.append(in_call)
stmts.append(Comment())
# Call verifier
if requires_proof:
verifier = IdentifierExpr(
cfg.get_contract_var_name(
ext_circuit.verifier_contract_type.code()))
verifier_args = [
IdentifierExpr(cfg.proof_param_name),
IdentifierExpr(cfg.zk_in_name),
IdentifierExpr(cfg.zk_out_name)
]
verify = ExpressionStatement(
verifier.call(cfg.verification_function_name, verifier_args))
stmts.append(
StatementList(
[Comment('Verify zk proof of execution'), verify],
excluded_from_simulation=True))
# Add return statement at the end if necessary
if int_fct.return_parameters:
stmts.append(
ReturnStatement(
TupleExpr([
IdentifierExpr(vd.idf.clone())
for vd in int_fct.return_var_decls
])))
return Block(stmts)
def visitExpression(self, ast: Expression):
parent = ast
while parent and not isinstance(parent, Statement):
parent = parent.parent
if parent:
ast.statement = parent
def add_to_circuit_inputs(self, expr: Expression) -> HybridArgumentIdf:
"""
Add the provided expression to the public circuit inputs.
Roughly corresponds to in() from paper
If expr is encrypted (privacy != @all), this function also automatically ensures that the circuit has access to
the correctly decrypted expression value in the form of a new private circuit input.
If expr is an IdentifierExpr, its value will be cached
(i.e. when the same identifier is needed again as a circuit input, its value will be retrieved from cache rather \
than adding an expensive redundant input. The cache is invalidated as soon as the identifier is overwritten in public code)
Note: This function has side effects on expr.statement (adds a pre_statement)
:param expr: [SIDE EFFECT] expression which should be made available inside the circuit as an argument
:return: HybridArgumentIdf which references the plaintext value of the newly added input
"""
privacy = expr.annotated_type.privacy_annotation.privacy_annotation_label(
) if expr.annotated_type.is_private() else Expression.all_expr()
is_public = privacy == Expression.all_expr()
expr_text = expr.code()
input_expr = self._expr_trafo.visit(expr)
t = input_expr.annotated_type.type_name
locally_decrypted_idf = None
# If expression has literal type -> evaluate it inside the circuit (constant folding will be used)
# rather than introducing an unnecessary public circuit input (expensive)
if isinstance(t, BooleanLiteralType):
return self._evaluate_private_expression(input_expr, str(t.value))
elif isinstance(t, NumberLiteralType):
return self._evaluate_private_expression(input_expr, str(t.value))
t_suffix = ''
if isinstance(expr, IdentifierExpr):
# Look in cache before doing expensive move-in
if self._remapper.is_remapped(expr.target.idf):
remapped_idf = self._remapper.get_current(expr.target.idf)
return remapped_idf
t_suffix = f'_{expr.idf.name}'
# Generate circuit inputs
if is_public:
tname = f'{self._in_name_factory.get_new_name(expr.annotated_type.type_name)}{t_suffix}'
return_idf = input_idf = self._in_name_factory.add_idf(
tname, expr.annotated_type.type_name)
self._phi.append(CircComment(f'{input_idf.name} = {expr_text}'))
else:
# Encrypted inputs need to be decrypted inside the circuit (i.e. add plain as private input and prove encryption)
tname = f'{self._secret_input_name_factory.get_new_name(expr.annotated_type.type_name)}{t_suffix}'
return_idf = locally_decrypted_idf = self._secret_input_name_factory.add_idf(
tname, expr.annotated_type.type_name)
cipher_t = TypeName.cipher_type(input_expr.annotated_type,
expr.annotated_type.homomorphism)
tname = f'{self._in_name_factory.get_new_name(cipher_t)}{t_suffix}'
input_idf = self._in_name_factory.add_idf(
tname, cipher_t, IdentifierExpr(locally_decrypted_idf))
# Add a CircuitInputStatement to the solidity code, which looks like a normal assignment statement,
# but also signals the offchain simulator to perform decryption if necessary
expr.statement.pre_statements.append(
CircuitInputStatement(input_idf.get_loc_expr(), input_expr))
if not is_public:
# Check if the secret plain input corresponds to the decrypted cipher value
crypto_params = cfg.get_crypto_params(
expr.annotated_type.homomorphism)
self._phi.append(
CircComment(
f'{locally_decrypted_idf} = dec({expr_text}) [{input_idf.name}]'
))
self._ensure_encryption(expr.statement, locally_decrypted_idf,
Expression.me_expr(), crypto_params,
input_idf, False, True)
# Cache circuit input for later reuse if possible
if cfg.opt_cache_circuit_inputs and isinstance(expr, IdentifierExpr):
# TODO: What if a homomorphic variable gets used as both a plain variable and as a ciphertext?
# This works for now because we never perform homomorphic operations on variables we can decrypt.
self._remapper.remap(expr.target.idf, return_idf)
return return_idf
def _get_circuit_output_for_private_expression(
self, expr: Expression, new_privacy: PrivacyLabelExpr,
homomorphism: Homomorphism) -> LocationExpr:
"""
Add evaluation of expr to the circuit and return the output HybridArgumentIdf corresponding to the evaluation result.
Note: has side effects on expr.statement (adds pre_statement)
:param expr: [SIDE EFFECT] expression to evaluate
:param new_privacy: result owner (determines encryption key)
:return: HybridArgumentIdf which references the circuit output containing the result of expr
"""
is_circ_val = isinstance(expr, IdentifierExpr) and isinstance(
expr.idf, HybridArgumentIdf
) and expr.idf.arg_type != HybridArgType.PUB_CONTRACT_VAL
is_hom_comp = isinstance(expr, FunctionCallExpr) and isinstance(
expr.func, BuiltinFunction
) and expr.func.homomorphism != Homomorphism.NON_HOMOMORPHIC
if is_hom_comp:
# Treat a homomorphic operation as a privately evaluated operation on (public) ciphertexts
expr.annotated_type = AnnotatedTypeName.cipher_type(
expr.annotated_type, homomorphism)
if is_circ_val or expr.annotated_type.is_private(
) or expr.evaluate_privately:
priv_result_idf = self._evaluate_private_expression(expr)
else:
# For public expressions which should not be evaluated in private, only the result is moved into the circuit
priv_result_idf = self.add_to_circuit_inputs(expr)
private_expr = priv_result_idf.get_idf_expr()
t_suffix = ''
if isinstance(expr, IdentifierExpr) and not is_circ_val:
t_suffix += f'_{expr.idf.name}'
if isinstance(new_privacy,
AllExpr) or expr.annotated_type.type_name.is_cipher():
# If the result is public, add an equality constraint to ensure that the user supplied public output
# is equal to the circuit evaluation result
tname = f'{self._out_name_factory.get_new_name(expr.annotated_type.type_name)}{t_suffix}'
new_out_param = self._out_name_factory.add_idf(
tname, expr.annotated_type.type_name, private_expr)
self._phi.append(CircEqConstraint(priv_result_idf, new_out_param))
out_var = new_out_param.get_loc_expr().explicitly_converted(
expr.annotated_type.type_name)
else:
# If the result is encrypted, add an encryption constraint to ensure that the user supplied encrypted output
# is equal to the correctly encrypted circuit evaluation result
new_privacy = self._get_canonical_privacy_label(
expr.analysis, new_privacy)
privacy_label_expr = get_privacy_expr_from_label(new_privacy)
cipher_t = TypeName.cipher_type(expr.annotated_type, homomorphism)
tname = f'{self._out_name_factory.get_new_name(cipher_t)}{t_suffix}'
enc_expr = EncryptionExpression(private_expr, privacy_label_expr,
homomorphism)
new_out_param = self._out_name_factory.add_idf(
tname, cipher_t, enc_expr)
crypto_params = cfg.get_crypto_params(homomorphism)
self._ensure_encryption(expr.statement, priv_result_idf,
new_privacy, crypto_params, new_out_param,
False, False)
out_var = new_out_param.get_loc_expr()
# Add an invisible CircuitComputationStatement to the solidity code, which signals the offchain simulator,
# that the value the contained out variable must be computed at this point by simulating expression evaluation
expr.statement.pre_statements.append(
CircuitComputationStatement(new_out_param))
return out_var
def evaluate_stmt_in_circuit(self, ast: Statement) -> AssignmentStatement:
"""
Evaluate an entire statement privately.
This works by turning the statement into an assignment statement where the
* lhs is a tuple of all external locations (defined outside statement), which are modified inside the statement
* rhs is the return value of an inlined function call expression to a virtual function where body = the statement + return statement \
which returns a tuple of the most recent SSA version of all modified locations
Note: Modifying external locations which are not owned by @me inside the statement is illegal (would leak information).
Note: At the moment, this is only used for if statements with a private condition.
:param ast: the statement to evaluate inside the circuit
:return: AssignmentStatement as described above
"""
astmt = ExpressionStatement(NumberLiteralExpr(0))
for var in ast.modified_values:
if var.in_scope_at(ast):
astmt = AssignmentStatement(None, None)
break
astmt.before_analysis = ast.before_analysis
# External values written inside statement -> function return values
ret_params = []
for var in ast.modified_values:
if var.in_scope_at(ast):
# side effect affects location outside statement and has privacy @me
assert ast.before_analysis.same_partition(
var.privacy, Expression.me_expr())
assert isinstance(
var.target,
(Parameter, VariableDeclaration, StateVariableDeclaration))
t = var.target.annotated_type.zkay_type
if not t.type_name.is_primitive_type():
raise NotImplementedError(
'Reference types inside private if statements are not supported'
)
ret_t = AnnotatedTypeName(t.type_name, Expression.me_expr(),
t.homomorphism) # t, but @me
ret_param = IdentifierExpr(var.target.idf.clone(),
ret_t).override(target=var.target)
ret_param.statement = astmt
ret_params.append(ret_param)
# Build the imaginary function
fdef = ConstructorOrFunctionDefinition(
Identifier('<stmt_fct>'), [], ['private'], [
Parameter([], ret.annotated_type, ret.target.idf)
for ret in ret_params
], Block([ast, ReturnStatement(TupleExpr(ret_params))]))
fdef.original_body = fdef.body
fdef.body.parent = fdef
fdef.parent = ast
# inline "Call" to the imaginary function
fcall = FunctionCallExpr(
IdentifierExpr('<stmt_fct>').override(target=fdef), [])
fcall.statement = astmt
ret_args = self.inline_function_call_into_circuit(fcall)
# Move all return values out of the circuit
if not isinstance(ret_args, TupleExpr):
ret_args = TupleExpr([ret_args])
for ret_arg in ret_args.elements:
ret_arg.statement = astmt
ret_arg_outs = [
self._get_circuit_output_for_private_expression(
ret_arg, Expression.me_expr(),
ret_param.annotated_type.homomorphism)
for ret_param, ret_arg in zip(ret_params, ret_args.elements)
]
# Create assignment statement
if ret_params:
astmt.lhs = TupleExpr(
[ret_param.clone() for ret_param in ret_params])
astmt.rhs = TupleExpr(ret_arg_outs)
return astmt
else:
assert isinstance(astmt, ExpressionStatement)
return astmt
def transform_contract(self, su: SourceUnit, c: ContractDefinition) -> ContractDefinition:
"""
Transform an entire zkay contract into a public solidity contract.
This:
* transforms state variables, function bodies and signatures
* import verification contracts
* adds zk_data structs for each function with verification \
(to store circuit I/O, to bypass solidity stack limit and allow for easy assignment of array variables),
* creates external wrapper functions for all public functions which require verification
* adds circuit IO serialization/deserialization code from/to zk_data struct to all functions which require verification.
:param su: [SIDE EFFECTS] Source unit of which this contract is part of
:param c: [SIDE EFFECTS] The contract to transform
:return: The contract itself
"""
all_fcts = c.constructor_definitions + c.function_definitions
# Get list of static owner labels for this contract
global_owners = [Expression.me_expr()]
for var in c.state_variable_declarations:
if var.annotated_type.is_address() and (var.is_final or var.is_constant):
global_owners.append(var.idf)
# Backup untransformed function bodies
for fct in all_fcts:
fct.original_body = deep_copy(fct.body, with_types=True, with_analysis=True)
# Transform types of normal state variables
c.state_variable_declarations = self.var_decl_trafo.visit_list(c.state_variable_declarations)
# Split into functions which require verification and those which don't need a circuit helper
req_ext_fcts = {}
new_fcts, new_constr = [], []
for fct in all_fcts:
assert isinstance(fct, ConstructorOrFunctionDefinition)
if fct.requires_verification or fct.requires_verification_when_external:
self.circuits[fct] = self.create_circuit_helper(fct, global_owners)
if fct.requires_verification_when_external:
req_ext_fcts[fct] = fct.parameters[:]
elif fct.is_constructor:
new_constr.append(fct)
else:
new_fcts.append(fct)
# Add constant state variables for external contracts and field prime
field_prime_decl = StateVariableDeclaration(AnnotatedTypeName.uint_all(), ['public', 'constant'],
Identifier(cfg.field_prime_var_name),
NumberLiteralExpr(bn128_scalar_field))
contract_var_decls = self.include_verification_contracts(su, c)
c.state_variable_declarations = [field_prime_decl, Comment()]\
+ Comment.comment_list('Helper Contracts', contract_var_decls)\
+ [Comment('User state variables')]\
+ c.state_variable_declarations
# Transform signatures
for f in all_fcts:
f.parameters = self.var_decl_trafo.visit_list(f.parameters)
for f in c.function_definitions:
f.return_parameters = self.var_decl_trafo.visit_list(f.return_parameters)
f.return_var_decls = self.var_decl_trafo.visit_list(f.return_var_decls)
# Transform bodies
for fct in all_fcts:
gen = self.circuits.get(fct, None)
fct.body = ZkayStatementTransformer(gen).visit(fct.body)
# Transform (internal) functions which require verification (add the necessary additional parameters and boilerplate code)
fcts_with_verification = [fct for fct in all_fcts if fct.requires_verification]
compute_transitive_circuit_io_sizes(fcts_with_verification, self.circuits)
transform_internal_calls(fcts_with_verification, self.circuits)
for f in fcts_with_verification:
circuit = self.circuits[f]
assert circuit.requires_verification()
if circuit.requires_zk_data_struct():
# Add zk data struct for f to contract
zk_data_struct = StructDefinition(Identifier(circuit.zk_data_struct_name), [
VariableDeclaration([], AnnotatedTypeName(idf.t), idf.clone(), '')
for idf in circuit.output_idfs + circuit.input_idfs
])
c.struct_definitions.append(zk_data_struct)
self.create_internal_verification_wrapper(f)
# Create external wrapper functions where necessary
for f, params in req_ext_fcts.items():
ext_f, int_f = self.split_into_external_and_internal_fct(f, params, global_owners)
if ext_f.is_function:
new_fcts.append(ext_f)
else:
new_constr.append(ext_f)
new_fcts.append(int_f)
c.constructor_definitions = new_constr
c.function_definitions = new_fcts
return c
def visitFunctionCallExpr(self, ast: FunctionCallExpr):
if isinstance(ast.func, BuiltinFunction):
if ast.func.is_private:
"""
Modified Rule (12) builtin functions with private operands are evaluated inside the circuit.
A private expression on its own (like an IdentifierExpr referring to a private variable) is not enough to trigger a
boundary crossing (assignment of private variables is a public operation).
"""
return self.gen.evaluate_expr_in_circuit(ast, Expression.me_expr())
else:
"""
Rule (10) with additional short-circuit handling.
Builtin operations on public operands are normally left untransformed, but if the builtin function has
short-circuiting semantics, guard conditions must be added if any of the public operands contains
nested private expressions.
"""
# handle short-circuiting
if ast.func.has_shortcircuiting() and any(map(contains_private_expr, ast.args[1:])):
op = ast.func.op
guard_var = self.gen.add_to_circuit_inputs(ast.args[0])
ast.args[0] = guard_var.get_loc_expr(ast)
if op == 'ite':
ast.args[1] = self.visit_guarded_expression(guard_var, True, ast.args[1])
ast.args[2] = self.visit_guarded_expression(guard_var, False, ast.args[2])
elif op == '||':
ast.args[1] = self.visit_guarded_expression(guard_var, False, ast.args[1])
elif op == '&&':
ast.args[1] = self.visit_guarded_expression(guard_var, True, ast.args[1])
return ast
return self.visit_children(ast)
elif ast.is_cast:
"""Casts are handled either in public or inside the circuit depending on the privacy of the casted expression."""
assert isinstance(ast.func.target, EnumDefinition)
if ast.args[0].evaluate_privately:
return self.gen.evaluate_expr_in_circuit(ast, Expression.me_expr())
else:
return self.visit_children(ast)
else:
"""
Handle normal function calls (outside private expression case).
The called functions are allowed to have side effects,
if the function does not require verification it can even be recursive.
"""
assert isinstance(ast.func, LocationExpr)
ast = self.visit_children(ast)
if ast.func.target.requires_verification_when_external:
# Reroute the function call to the corresponding internal function if the called function was split into external/internal.
if not isinstance(ast.func, IdentifierExpr):
raise NotImplementedError()
ast.func.idf.name = cfg.get_internal_name(ast.func.target)
if ast.func.target.requires_verification:
# If the target function has an associated circuit, make this function's circuit aware of the call.
self.gen.call_function(ast)
elif ast.func.target.has_side_effects and self.gen is not None:
# Invalidate modified state variables for the current circuit
for val in ast.modified_values:
if val.key is None and isinstance(val.target, StateVariableDeclaration):
self.gen.invalidate_idf(val.target.idf)
# The call will be present as a normal function call in the output solidity code.
return ast
def visitPrimitiveCastExpr(self, ast: PrimitiveCastExpr):
"""Casts are handled either in public or inside the circuit depending on the privacy of the casted expression."""
if ast.evaluate_privately:
return self.gen.evaluate_expr_in_circuit(ast, Expression.me_expr())
else:
return self.visit_children(ast)
def visitExpression(self, ast: Expression):
self.visit_child_expressions(ast, ast.children())
def create_external_wrapper_body(int_fct: ConstructorOrFunctionDefinition, ext_circuit: CircuitHelper,
original_params: List[Parameter], requires_proof: bool) -> Block:
"""
Return Block with external wrapper function body.
:param int_fct: corresponding internal function
:param ext_circuit: [SIDE EFFECT] circuit helper of the external wrapper function
:param original_params: list of transformed function parameters without additional parameters added due to transformation
:return: body with wrapper code
"""
priv_args = [p for p in original_params if p.annotated_type.is_cipher()]
args_backends = OrderedDict.fromkeys([p.annotated_type.type_name.crypto_params for p in priv_args])
stmts = []
for crypto_params in args_backends:
assert crypto_params in int_fct.used_crypto_backends
# If there are any private arguments with homomorphism 'hom', we need the public key for that crypto backend
ext_circuit._require_public_key_for_label_at(None, Expression.me_expr(), crypto_params)
for crypto_params in cfg.all_crypto_params():
if crypto_params.is_symmetric_cipher():
if (MeExpr(), crypto_params) in ext_circuit.requested_global_keys or crypto_params in args_backends:
# Make sure msg.sender's key pair is available in the circuit
stmts += ext_circuit.request_private_key(crypto_params)
# Verify that out parameter has correct size
stmts += [RequireStatement(IdentifierExpr(cfg.zk_out_name).dot('length').binop('==', NumberLiteralExpr(ext_circuit.out_size_trans)))]
# IdentifierExpr for array var holding serialized public circuit inputs
in_arr_var = IdentifierExpr(cfg.zk_in_name).as_type(Array(AnnotatedTypeName.uint_all()))
# Request static public keys
offset = 0
key_req_stmts = []
me_key_idx: Dict[CryptoParams, int] = {}
if ext_circuit.requested_global_keys:
# Ensure that me public key is stored starting at in[0]
keys = [key for key in ext_circuit.requested_global_keys]
tmp_keys = {}
for crypto_params in int_fct.used_crypto_backends:
tmp_key_var = Identifier(f'_tmp_key_{crypto_params.identifier_name}')
key_req_stmts.append(tmp_key_var.decl_var(AnnotatedTypeName.key_type(crypto_params)))
tmp_keys[crypto_params] = tmp_key_var
for (key_owner, crypto_params) in keys:
tmp_key_var = tmp_keys[crypto_params]
idf, assignment = ext_circuit.request_public_key(crypto_params, key_owner, ext_circuit.get_glob_key_name(key_owner, crypto_params))
assignment.lhs = IdentifierExpr(tmp_key_var.clone())
key_req_stmts.append(assignment)
# Remember me-keys for later use in symmetrically encrypted keys
if key_owner == MeExpr():
assert crypto_params not in me_key_idx
me_key_idx[crypto_params] = offset
# Manually add to circuit inputs
key_len = crypto_params.key_len
key_req_stmts.append(in_arr_var.slice(offset, key_len).assign(IdentifierExpr(tmp_key_var.clone()).slice(0, key_len)))
offset += key_len
assert offset == ext_circuit.in_size
# Check encrypted parameters
param_stmts = []
for p in original_params:
""" * of T_e rule 8 """
if p.annotated_type.is_cipher():
cipher_payload_len = p.annotated_type.type_name.crypto_params.cipher_payload_len
assign_stmt = in_arr_var.slice(offset, cipher_payload_len).assign(IdentifierExpr(p.idf.clone()).slice(0, cipher_payload_len))
ext_circuit.ensure_parameter_encryption(assign_stmt, p)
# Manually add to circuit inputs
param_stmts.append(assign_stmt)
offset += cipher_payload_len
# Populate sender field of parameters encrypted with a symmetric cipher
copy_stmts = []
for p in original_params:
if p.annotated_type.is_cipher():
c = p.annotated_type.type_name
assert isinstance(c, CipherText)
if c.crypto_params.is_symmetric_cipher():
sender_key = in_arr_var.index(me_key_idx[c.crypto_params])
idf = IdentifierExpr(p.idf.clone()).as_type(p.annotated_type.clone())
cipher_payload_len = cfg.get_crypto_params(p.annotated_type.homomorphism).cipher_payload_len
lit = ArrayLiteralExpr([idf.clone().index(i) for i in range(cipher_payload_len)] + [sender_key])
copy_stmts.append(VariableDeclarationStatement(VariableDeclaration([], p.annotated_type.clone(), p.idf.clone(), 'memory'), lit))
if copy_stmts:
param_stmts += [Comment(), Comment('Copy from calldata to memory and set sender field')] + copy_stmts
# Declare in array
new_in_array_expr = NewExpr(AnnotatedTypeName(TypeName.dyn_uint_array()), [NumberLiteralExpr(ext_circuit.in_size_trans)])
in_var_decl = in_arr_var.idf.decl_var(TypeName.dyn_uint_array(), new_in_array_expr)
stmts.append(in_var_decl)
stmts.append(Comment())
stmts += Comment.comment_wrap_block('Request static public keys', key_req_stmts)
stmts += Comment.comment_wrap_block('Backup private arguments for verification', param_stmts)
# Call internal function
args = [IdentifierExpr(param.idf.clone()) for param in original_params]
internal_call = FunctionCallExpr(IdentifierExpr(int_fct.idf.clone()).override(target=int_fct), args)
internal_call.sec_start_offset = ext_circuit.priv_in_size
if int_fct.requires_verification:
ext_circuit.call_function(internal_call)
args += [in_arr_var.clone(), NumberLiteralExpr(ext_circuit.in_size),
IdentifierExpr(cfg.zk_out_name), NumberLiteralExpr(ext_circuit.out_size)]
if int_fct.return_parameters:
stmts += Comment.comment_list("Declare return variables", [VariableDeclarationStatement(deep_copy(vd)) for vd in int_fct.return_var_decls])
in_call = TupleExpr([IdentifierExpr(vd.idf.clone()) for vd in int_fct.return_var_decls]).assign(internal_call)
else:
in_call = ExpressionStatement(internal_call)
stmts.append(Comment("Call internal function"))
stmts.append(in_call)
stmts.append(Comment())
# Call verifier
if requires_proof and not cfg.disable_verification:
verifier = IdentifierExpr(cfg.get_contract_var_name(ext_circuit.verifier_contract_type.code()))
verifier_args = [IdentifierExpr(cfg.proof_param_name), IdentifierExpr(cfg.zk_in_name), IdentifierExpr(cfg.zk_out_name)]
verify = ExpressionStatement(verifier.call(cfg.verification_function_name, verifier_args))
stmts.append(StatementList([Comment('Verify zk proof of execution'), verify], excluded_from_simulation=True))
# Add return statement at the end if necessary
if int_fct.return_parameters:
stmts.append(ReturnStatement(TupleExpr([IdentifierExpr(vd.idf.clone()) for vd in int_fct.return_var_decls])))
return Block(stmts)
def visitExpression(self, ast: Expression):
assert self.evaluate_privately is not None
ast.evaluate_privately = self.evaluate_privately
self.visitChildren(ast)
