27 lines
970 B
Ada
27 lines
970 B
Ada
with Ada.Text_IO, Ada.Command_Line, Crypto.Types.Big_Numbers;
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procedure Mod_Exp is
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A: String :=
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"2988348162058574136915891421498819466320163312926952423791023078876139";
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B: String :=
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"2351399303373464486466122544523690094744975233415544072992656881240319";
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D: constant Positive := Positive'Max(Positive'Max(A'Length, B'Length), 40);
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-- the number of decimals to store A, B, and result
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Bits: constant Positive := (34*D)/10;
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-- (slightly more than) the number of bits to store A, B, and result
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package LN is new Crypto.Types.Big_Numbers (Bits + (32 - Bits mod 32));
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-- the actual number of bits has to be a multiple of 32
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use type LN.Big_Unsigned;
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function "+"(S: String) return LN.Big_Unsigned
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renames LN.Utils.To_Big_Unsigned;
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M: LN.Big_Unsigned := (+"10") ** (+"40");
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begin
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Ada.Text_IO.Put("A**B (mod 10**40) = ");
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Ada.Text_IO.Put_Line(LN.Utils.To_String(LN.Mod_Utils.Pow((+A), (+B), M)));
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end Mod_Exp;
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