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eucrypt_ch10_oaep...    1 -- Implementation of TMSR's OAEP with Keccak as hash function
eucrypt_ch10_oaep...    2 --
eucrypt_ch10_oaep...    3 -- S.MG, 2018
eucrypt_ch10_oaep...    4 
eucrypt_ch10_oaep...    5 with SMG_Keccak; use SMG_Keccak; -- Keccak is used as hash function
eucrypt_ch10_oaep...    6 with Interfaces; use Interfaces; -- for Unsigned_8 type and bit-level ops
eucrypt_ch10_oaep...    7 with Interfaces.C; use Interfaces.C; -- for interop with C
eucrypt_ch10_oaep...    8 
eucrypt_ch10_oaep...    9 package SMG_OAEP is
eucrypt_ch10_oaep...   10   pragma Pure( SMG_OAEP ); -- stateless, no side effects -> can cache calls
eucrypt_ch10_oaep...   11 
eucrypt_ch10_oaep...   12   -- fixed length of OAEP block in bits and in octets
eucrypt_ch10_oaep...   13   OAEP_LENGTH_BITS   : constant := 4096;
eucrypt_ch10_oaep...   14   OAEP_LENGTH_OCTETS : constant := 512;
eucrypt_ch10_oaep...   15   OAEP_HALF_OCTETS   : constant := OAEP_LENGTH_OCTETS / 2;
eucrypt_oaep_fix_...   16   TMSR               : constant String := "TMSR-RSA";
eucrypt_ch12_wrap...   17   MAX_LEN_MSG        : constant Natural := OAEP_HALF_OCTETS - TMSR'Length - 3;
eucrypt_ch12_wrap...   18   pragma Export( C, MAX_LEN_MSG, "max_len_msg"); -- to be accessed from rsa.c
eucrypt_ch10_oaep...   19 
eucrypt_ch10_oaep...   20   -- subtypes used by the OAEP encrypt/decrypt
eucrypt_ch10_oaep...   21   subtype OAEP_Block is String( 1 .. OAEP_LENGTH_OCTETS );
eucrypt_ch10_oaep...   22   subtype OAEP_HALF is String( 1 .. OAEP_HALF_OCTETS );
eucrypt_ch10_oaep...   23 
eucrypt_ch12_wrap...   24   -- copy from Ada String to C char array and back, octet by octet
eucrypt_ch12_wrap...   25 
eucrypt_ch12_wrap...   26   -- This copies first Len characters from A to the first Len positions in S
eucrypt_ch12_wrap...   27   -- NB: this does NOT allocate /check memory!
eucrypt_ch12_wrap...   28   -- Caller has to ensure that:
eucrypt_ch12_wrap...   29   --    S has space for at least Len characters
eucrypt_ch12_wrap...   30   --    A has at least Len characters
eucrypt_ch12_wrap...   31   procedure Char_Array_To_String( A   : in Interfaces.C.char_array;
eucrypt_ch12_wrap...   32                                   Len : in Natural;
eucrypt_ch12_wrap...   33                                   S   : out String);
eucrypt_ch12_wrap...   34 
eucrypt_ch12_wrap...   35   -- This copies first Len characters from S to the first Len positions in A
eucrypt_ch12_wrap...   36   -- NB: there are NO checks or memory allocations here!
eucrypt_ch12_wrap...   37   -- Caller has to make sure that:
eucrypt_ch12_wrap...   38   --   S'Length >= Len
eucrypt_ch12_wrap...   39   --   A has allocated space for at least Len characters
eucrypt_ch12_wrap...   40   procedure String_To_Char_Array( S   : in String;
eucrypt_ch12_wrap...   41                                   Len : in Natural;
eucrypt_ch12_wrap...   42                                   A   : out Interfaces.C.char_array);
eucrypt_ch12_wrap...   43 
eucrypt_ch10_oaep...   44   -- padding & formatting of maximum 1960 bits of the given String 
eucrypt_ch10_oaep...   45   -- uses TMSR's OAEP schema:
eucrypt_ch10_oaep...   46   -- 1.format M00 as: [random octet][sz1][sz2]"TMSR-RSA"[random]*Message
eucrypt_ch10_oaep...   47   --    where sz1 and sz2 store the length of the message in bits
eucrypt_ch10_oaep...   48   --    the random octets before message are padding to make OAEP_LENGTH_OCTETS
eucrypt_ch10_oaep...   49   -- 2. R = OAEP_HALF_OCTETS random bits
eucrypt_ch10_oaep...   50   -- 3. X = M00 xor hash(R)
eucrypt_ch10_oaep...   51   -- 4. Y = R xor hash(X)
eucrypt_ch10_oaep...   52   -- 5. Result is X || Y 
eucrypt_ch10_oaep...   53   -- NB: the Entropy parameter should be random octets from which this method 
eucrypt_ch10_oaep...   54   -- will use as many as required for the OAEP encryption of given Msg
eucrypt_oaep_fix_...   55   -- NB: at MOST MAX_LEN_MSG octets of Msg! (Msg at most 1960 bits)
eucrypt_ch12_wrap...   56   procedure OAEP_Encrypt( Msg      : in String;
eucrypt_ch12_wrap...   57                           Entropy  : in OAEP_Block;
eucrypt_ch12_wrap...   58                           Output   : out OAEP_Block);
eucrypt_ch12_wrap...   59 
eucrypt_ch12_wrap...   60 
eucrypt_ch12_wrap...   61   -- wrapper of oaep_encrypt for direct use from C
eucrypt_ch12_wrap...   62   -- NB: caller HAS TO provide the length of the Message (parameter LenMsg)
eucrypt_ch12_wrap...   63   -- NB: caller HAS TO provide the length of the Entropy (parameter LenEnt)
eucrypt_ch12_wrap...   64   -- NB: caller HAS TO provide the allocated space for result (LenEncr)
eucrypt_ch12_wrap...   65   -- NB: LenEncr HAS TO be at least OAEP_LENGTH_OCTETS!
eucrypt_ch12_wrap...   66   -- NB: LenEnt HAS TO be at least OAEP_LENGTH_OCTETS or this will FAIL!
eucrypt_ch12_wrap...   67   procedure OAEP_Encrypt_C( Msg       : in Interfaces.C.char_array;
eucrypt_ch12_wrap...   68                             MsgLen    : in Interfaces.C.size_t;
eucrypt_ch12_wrap...   69                             Entropy   : in Interfaces.C.char_array;
eucrypt_ch12_wrap...   70                             EntLen    : in Interfaces.C.size_t;
eucrypt_ch12_wrap...   71                             Encr      : out Interfaces.C.char_array;
eucrypt_ch12_wrap...   72                             EncrLen   : in Interfaces.C.size_t;
eucrypt_ch12_wrap...   73                             Success   : out Interfaces.C.Int);
eucrypt_ch12_wrap...   74   pragma Export( C, OAEP_Encrypt_C, "oaep_encrypt_c" );
eucrypt_ch10_oaep...   75 
eucrypt_ch10_oaep...   76   -- This is the opposite of OAEP_Encrypt above.
eucrypt_ch10_oaep...   77   -- @param Encr - an OAEP block previously obtained from OAEP_Encrypt
eucrypt_ch10_oaep...   78   -- @param Len - this will hold the length of the obtained message (in bits!)
eucrypt_ch10_oaep...   79   -- @param Output - the first Len octets of this are the recovered message
eucrypt_ch10_oaep...   80   -- @param Success - set to TRUE if message was recovered, false otherwise
eucrypt_ch10_oaep...   81   -- NB: when Success is FALSE, both Len and Output have undefined values
eucrypt_ch10_oaep...   82   procedure OAEP_Decrypt( Encr    : in OAEP_Block;
eucrypt_ch10_oaep...   83                           Len     : out Natural;
eucrypt_ch10_oaep...   84                           Output  : out OAEP_HALF;
eucrypt_ch10_oaep...   85                           Success : out Boolean);
eucrypt_ch10_oaep...   86 
eucrypt_ch12_wrap...   87   -- wrapper for use from C
eucrypt_ch12_wrap...   88   procedure oaep_decrypt_c( Encr    : in Interfaces.C.Char_Array;
eucrypt_ch12_wrap...   89                             EncrLen : in Interfaces.C.Int;
eucrypt_ch12_wrap...   90                             Decr    : out Interfaces.C.Char_Array;
eucrypt_ch12_wrap...   91                             DecrLen : in out Interfaces.C.Int;
eucrypt_ch12_wrap...   92                             Success : out Interfaces.C.Int);
eucrypt_ch12_wrap...   93   pragma Export( C, oaep_decrypt_c, "oaep_decrypt_c");
eucrypt_ch12_wrap...   94 
eucrypt_ch10_oaep...   95   -- helper method, xor on strings
eucrypt_ch10_oaep...   96   -- NB: only Output'Length bits will be considered from S1 and S2
eucrypt_ch10_oaep...   97   -- NB: caller is responsible for S1 and S2 being long enough!
eucrypt_ch10_oaep...   98   procedure XOR_Strings( S1: in String; S2: in String; Output: out String );
eucrypt_ch10_oaep...   99 
eucrypt_ch10_oaep...  100   -- gnat-specific methods for bit-level operations
eucrypt_ch10_oaep...  101 	function Shift_Right( Value  : Unsigned_8; 
eucrypt_ch10_oaep...  102                         Amount : Natural ) 
eucrypt_ch10_oaep...  103                         return Unsigned_8;
eucrypt_ch10_oaep...  104   pragma Import(Intrinsic, Shift_Right); 
eucrypt_ch10_oaep...  105 
eucrypt_ch10_oaep...  106 	function Shift_Left( Value  : Unsigned_8; 
eucrypt_ch10_oaep...  107                         Amount : Natural ) 
eucrypt_ch10_oaep...  108                         return Unsigned_8;
eucrypt_ch10_oaep...  109   pragma Import(Intrinsic, Shift_Left); 
eucrypt_ch10_oaep...  110 
eucrypt_ch16_byte...  111   -- conversions between bytestream and string
eucrypt_ch10_oaep...  112   -- NB: caller has to ensure correct size of output parameter! no checks here.
eucrypt_ch16_byte...  113   procedure ToString( B: in Bytestream; S: out String );
eucrypt_ch16_byte...  114   procedure ToBytestream( S: in String; B: out Bytestream );
eucrypt_ch10_oaep...  115 
eucrypt_ch10_oaep...  116   -- public wrapper for Sponge to use String for input/output
eucrypt_ch10_oaep...  117   procedure HashKeccak( Input     : in String;
eucrypt_ch10_oaep...  118                         Output    : out String;
eucrypt_ch16_byte...  119                         Block_Len : in Keccak_Rate := Default_Byterate);
eucrypt_ch10_oaep...  120 
eucrypt_ch16_byte...  121   -- wrapper for calling Keccak hashing from C, with DEFAULT byterate
eucrypt_ch10_oaep...  122   -- @param Input the input string, as array of characters (C style)
eucrypt_ch12_wrap...  123   -- @param LenIn the length of the input string (as number of OCTETS)
eucrypt_ch12_wrap...  124   -- @param LenOut the desired number of OCTETS to be returned as output
eucrypt_ch12_wrap...  125   -- @param Output array of at least LenOut characters; will contain the hash
eucrypt_ch10_oaep...  126   -- NB: caller HAS TO provide the length of the Input (parameter LenIn)
eucrypt_ch10_oaep...  127   -- NB: caller HAS TO provide the length of the Output (parameter LenOut)
eucrypt_ch12_wrap...  128   procedure Hash( Input     : in Interfaces.C.Char_Array;
eucrypt_ch12_wrap...  129                   LenIn     : in Interfaces.C.size_t;
eucrypt_ch12_wrap...  130                   LenOut    : in Interfaces.C.size_t;
eucrypt_ch12_wrap...  131                   Output    : out Interfaces.C.Char_Array);
eucrypt_ch10_oaep...  132   pragma Export( C, Hash, "hash" );
eucrypt_ch10_oaep...  133 
eucrypt_ch10_oaep...  134 end SMG_OAEP;