From: nowhere@never.at   
      
   Herbert Kleebauer posted :   
      
   >>> I had a two line decoding header:   
      
   >>> hD1X-s0P_kUHP0UxGWX4ax1y1ieimnfeinklddmemkjanmndnadmndnpbbn   
   >>> hhpbbnpljhoxolnhaigidpllnbkdnhlkfhlflefblffahfUebdfahhfkokh   
      
   >> I'll check this in more detail this time.   
      
   > Here the source of the two header lines:   
      
   let me convert it into hexcoders view first :)   
      
   > 0100: 68 3144      push 3144   
   > 0103: 58           pop ax   
   > 0104: 2d 3073      sub ax,3073   
   > 0107: 50           push ax   
   > 0108: 5f           pop di                ;di=00d1   
      
   > 0109: 6b 55 48 50  imul word [di+48],50  ;[0119] ;_30:   
   > 010d: 30 55 78     xor [di+78],dl        ;[0149]   
   > 0110: 47           inc di   
   > 0111: 57           push di   
   > 0112: 58           pop ax   
   > 0113: 34 61        xor al,61             ;cmp di, b3..00   
   > 0115: 78 31        js  +31               ;0148   
   > 0117: 79 31        jns +31               ;014a ;_50   
      
   > 0119: 69                  ;data set1   
   > 011a: 65 69 6d 6e 66 65   ;   
   > 0120: 69 6e 6b 6c         ;   
   > 0124: 64 64 6d 65 6d 6b   ;   
   > 012a: 6a 61 6e            ;   
   > 012d: 6d 6e 64 6e 61 64   ;   
   > 0133: 6d 6e 64            ;   
   > 0136: 6e 70 62 62 6e 0d   ;   
   > 013c: 0a 68 68            ;   
   > 013f: 70 62 62 6e 70 6c   ;   
   > 0145: 6a 68 6f            ;   
                               ;data set2   
   > 0148: 78                  ;_10: js (69*50)=d0 xor 6f=bf   
   > 0149: 6f                  ;_20: 0148 become "js 0109"   
   > 014a: 6c 6e 68 61 69 67   ;(65*50)=90 xor 6c=FC aka "CLD"   
   > 0150: 69 64 70 6c         ;_50:   
   > 0154: 6c 6e 62 6b 64 6e   ;   
   > 015a: 68 6c 6b            ;   
   > 015d: 66 68 6c 66 6c 65   ;   
   > 0163: 66 62 6c            ;   
   > 0166: 66 66 61 68 66 55   ;   
   > 016c: 65 62 64            ;   
   > 016f: 66 61 68 68 66 6b   ;   
   > 0175: 6f 6b 68            ;   
      
   Interesting method. Terje wanted to see another 2:1 algo. Here is one!   
      
   > Here the code which is generated at runtime by xor-ing (after the mul   
   > with $50) the two above data blocks (this is the decoding routine):   
      
   > 014a: fc           cld   
   > 014b: be 0178      mov si,0178   
   > 014e: 89 f7        mov di,si   
      
   > 0150: b9 0004      mov cx,4   
      
   > 0153: ac          lodsb   
   > 0154: 2c 2e       sub al,2e   
   > 0156: 72 fb       jc 153   
   > 0158: 74 1e       jz 178   
   > 015a: 48          dec ax   
   > 015b: 3c 0b       cmp al,0b   
   > 015d: 76 08       jbe 0167   
   > 015f: 2c 06       sub al,6   
   > 0161: 3c 25       cmp al,25   
   > 0163: 76 02       jbe 167   
   > 0165: 2c 06       sub al,6   
      
   > 0167: 66 c1 c8 06 ROR eax,6     ;   
   > 016b: 45          inc bp   
   > 016c: 45          inc bp   
   > 016d: e2 e4       loop 0153   
   > 016f: 66 c1 c8 08 ROR eax,8     ;   
   > 0173: 66 ab       stosq   
   > 0175: 4f          dec di   
   > 0176: eb d8       jmp 0150   
   > 0178:             ;start of a non-B64 4:3 string (decoded in place)   
      
   funny that this look a bit similar to what I have in my B64 decoder :)   
      
   >>> The binary following this two lines was encoded as 6 bits per byte   
   >>> using the characters a-z, A-Z, 0-9, @ and /.   
   >> this sounds like a predecessor of Base64.   
   > There is no advantage in using Base64 in an ascii binary.   
      
   yeah, it may be just good for Big Endian machines.   
      
   >> [...] copied to check on Annie Ascii in motion :)   
      
   > But we never got a movie from Beth or Laura.   
      
   yes, it's sad that we lost all our ASM-Ladies.   
      
   > PS: Laura has also write such an ascii binary converter. The website   
   > doesn't exist anymore, but here is a dissasembly of her code:   
      
   > https://groups.google.com/forum/#!msg/alt.msdos.batch/u4qgr2gF   
   QI/i6sG_H31TtsJ   
   > https://groups.google.com/forum/#!msg/alt.msdos.batch/u4qgr2gF   
   QI/fL8dSJzmbh8J   
      
   Thanks, I'll check it.   
   __   
   wolfgang   
      
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