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SPSS also supports what it calls “encrypted passwords.” These are not encrypted. They are encoded with a simple, fixed scheme. An encoded password is always a multiple of 2 characters long, and never longer than 20 characters. The characters in an encoded password are always in the graphic ASCII range 33 through 126. Each successive pair of characters in the password encodes a single byte in the plaintext password.
Use the following algorithm to decode a pair of characters:
2 ⇒ 2367 3 ⇒ 0145 47 ⇒ 89cd 56 ⇒ abef
2 ⇒ 139b 3 ⇒ 028a 47 ⇒ 46ce 56 ⇒ 57df
03cf ⇒ 0145 12de ⇒ 2367 478b ⇒ 89cd 569a ⇒ abef
03cf ⇒ 028a 12de ⇒ 139b 478b ⇒ 46ce 569a ⇒ 57df
Consider the encoded character pair ‘-|’. a is 0x2d and b is 0x7c, so ah is 2, bh is 7, al is 0xd, and bl is 0xc. ah means that the most significant four bits of the decoded character is 2, 3, 6, or 7, and bh means that they are 4, 6, 0xc, or 0xe. The single possibility in common is 6, so the most significant four bits are 6. Similarly, al means that the least significant four bits are 2, 3, 6, or 7, and bl means they are 0, 2, 8, or 0xa, so the least significant four bits are 2. The decoded character is therefore 0x62, the letter ‘b’.
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