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140 lines
3.1 KiB
Plaintext
140 lines
3.1 KiB
Plaintext
# sint: secret integers
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# see also https://mp-spdz.readthedocs.io/en/latest/Compiler.html#Compiler.types.sint
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# you can assign public numbers to sint
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a = sint(1)
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b = sint(2)
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def test(actual, expected):
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# you can reveal a number in order to print it
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actual = actual.reveal()
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print_ln('expected %s, got %s', expected, actual)
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# private inputs are read from Player-Data/Input-P<i>-0
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# or from standard input if using command-line option -I
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# see https://mp-spdz.readthedocs.io/en/latest/io.html for more options
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for i in 0, 1:
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print_ln('got %s from player %s', sint.get_input_from(i).reveal(), i)
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# some arithmetic works as expected
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test(a + b, 3)
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test(a * b, 2)
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test(a - b, -1)
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# Division can mean different things in different domains
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# and there has be a specified bit length in some,
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# so we use int_div() for integer division.
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# k-bit division requires (4k+1)-bit computation.
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test(b.int_div(a, 15), 2)
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# comparisons produce 1 for true and 0 for false
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test(a < b, 1)
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test(a <= b, 1)
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test(a >= b, 0)
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test(a > b, 0)
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test(a == b, 0)
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test(a != b, 1)
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# if_else() can be used instead of branching
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# let's find out the larger number
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test((a < b).if_else(b, a), 2)
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# arrays and loops work as follows
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a = Array(100, sint)
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@for_range(100)
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def f(i):
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a[i] = sint(i) * sint(i - 1)
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test(a[99], 99 * 98)
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# if you use loops, use Array to store results
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# don't do this
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# @for_range(100)
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# def f(i):
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# a = sint(i)
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# test(a, 99)
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# sfix: fixed-point numbers
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# see also https://mp-spdz.readthedocs.io/en/latest/Compiler.html#Compiler.types.sfix
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# set the precision after the dot and in total
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sfix.set_precision(16, 31)
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# and the output precision in decimal digits
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print_float_precision(4)
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# you can do all basic arithmetic with sfix, including division
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a = sfix(2)
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b = sfix(-0.1)
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test(a + b, 1.9)
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test(a - b, 2.1)
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test(a * b, -0.2)
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test(a / b, -20)
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test(a < b, 0)
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test(a <= b, 0)
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test(a >= b, 1)
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test(a > b, 1)
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test(a == b, 0)
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test(a != b, 1)
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test((a < b).if_else(a, b), -0.1)
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# now let's do a computation with private inputs
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# party 0 supplies three number and party 1 supplies three percentages
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# we want to compute the weighted mean
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print_ln('Party 0: please input three numbers not adding up to zero')
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print_ln('Party 1: please input any three numbers')
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data = Matrix(3, 2, sfix)
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# use @for_range_opt for balanced optimization
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# but use Python loops if compile-time numbers are need (e.g., for players)
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@for_range_opt(3)
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def _(i):
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for j in range(2):
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data[i][j] = sfix.get_input_from(j)
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# compute weighted average
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weight_total = sum(point[0] for point in data)
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result = sum(point[0] * point[1] for point in data) / weight_total
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# branching is supported also depending on revealed secret data
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# with garbled circuits this triggers a interruption of the garbling
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@if_e((sum(point[0] for point in data) != 0).reveal())
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def _():
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print_ln('weighted average: %s', result.reveal())
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@else_
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def _():
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print_ln('your inputs made no sense')
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# permutation matrix
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M = Matrix(2, 2, sfix)
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M[0][0] = 0
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M[1][0] = 1
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M[0][1] = 1
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M[1][1] = 0
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# matrix multiplication
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M = data * M
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test(M[0][0], data[0][1].reveal())
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test(M[1][1], data[1][0].reveal())
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