OTP - One Time Password?
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OTP is mechanism witch can protect your password from eavesdropping on network
connection. On network is never sent your pasword, but only digest. Host system
doesn't known your pasword too.

Server:                            |      Client:
  challenge "otp-md5 202 seed"   ---->
                                   |        md5_digest:=md5(seed+password)
                                   |
  server known right answer for    |        for i:=0 to 202-1 do
  repeats count 499                |          md5_digest:=md5(md5_digest)
                                   |
                                 <----      64bit_to_6word(md5_digest)
  md5_digest:=6word_to_64bit       |
  for i:=202 to 499-1 do           |
    md5_digest:=md5(md5_digest)    |
                                   |
                                   |
  if result in md5_digest is same  |
  as serveres knowledge user is    |
  authorized if no user is refused |
                                   |
  for next login will user receive |
  challenge "otp-md5 201 seed"     |

SemTel's otp supports from rfc1938, algorithm md5 and md4 (not sha1). 'Extended
Responses' - rfc2243 aren't implemented.

references:
  rfc2289 A One-Time Password System. N. Haller, C. Metz, P. Nesser, M.
          Straw. February 1998. (Format: TXT=56495 bytes) (Obsoletes RFC1938)
          (Status: DRAFT STANDARD)
  rfc2243 OTP Extended Responses. C. Metz. November 1997. (Format:
          TXT=19730 bytes) (Status: PROPOSED STANDARD)
  rfc1938 A One-Time Password System. N. Haller & C. Metz. May 1996.
          (Format: TXT=44844 bytes) (Obsoleted by RFC2289) (Status: PROPOSED
          STANDARD)
  rfc1760 The S/KEY One-Time Password System. N. Haller. February 1995.
          (Format: TXT=31124 bytes) (Status: INFORMATIONAL)

  rfc1321 The MD5 Message-Digest Algorithm. R. Rivest. April 1992. (Format:
          TXT=35222 bytes) (Status: INFORMATIONAL)
  rfc1320 The MD4 Message-Digest Algorithm. R. Rivest. April 1992. (Format:
          TXT=32407 bytes) (Status: INFORMATIONAL)

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Document version : 0.902
Last change      : 23.8.1998
