user8209: In some of the tournaments I've been to, there were pretty indecent people (some of whose licenses were revoked).
One of my friends had a terrible incident. At the end of the game, he was dominating and his opponent looked at him, told him that he resigned, they shook hands and reset the pieces. When the referee came, their opponent claimed that they agreed for a draw.
Even though the referees asked the other players, they just said they shook hands and reset the pieces together. Naturally, cameras showed the very same thing. At the end of the day, he was not able to prove the fraud and lost half a point from an already won game.
A similar thing might be observed at the end of Carlsen's defeat against Anand in Dubai. What prevents Carlsen from claiming that they agreed to a draw?
Moreover, unfortunately, these types of frauds do not only occur in local tournaments. For instance, there was the game Tal vs. Adamski where Tal's wife saved the day.
Thus, my question is somewhat two-folded. How should one resign properly, and proceed when the opponent tells that they resign?

user13692: 1) When I resign, I usually do all of these: drop my king, say 'I resign', and stop the clocks, and offer a handshake. 
2) When my opponent says he resigns, I will not shake hands immediately, rather, I will stop the clocks and call the arbiter. After the arbiter comes, I will ask my opponent to state his resignation to the arbiter. 
Quod Erat Demonstrandum. 

user12523: The real question here does not seem to be how to resign, but how to deal with cheaters. There are ways of dealing with cheaters which are not specific to chess.
After the fact, some might suggest a fistfight, :-) while others might suggest social shaming (i.e., making sure everybody in the club/tournament learns that the person is a cheater). You can also request not to be paired against the cheater in the future. Tournament directors are not required to accommodate your request, but they can consider it. Finally, you can file a formal complaint, although there better be evidence.
Before the fact, you can either be "paranoid" about it (for example, by demanding that the director witness the resignation as someone else suggested), or you can relax and assume good faith knowing that cheating is very rare (unless you play in an environment very different from what I know!). Up to you.
In any case, keeping score is always advisable, for a variety of reasons.
Back to the incident in question: the tournament director has a lot of discretion when dealing with "ambiguous resignations" (ambiguous is how they look to a TD in a "he said, she said" situation). Here's what Tim Just, editor of the USCF rulebook, had to say about it in his book, Just Law:

If an ambiguous resignation is disputed promptly enough, then the game
  can simply continue. If the unclear resignation is not discovered
  until much later, then the waters get muddy. Some TDs like to award
  one point to the player who says they won the game and a half-point to
  the player who says they drew the same game—I am not a fan of this
  method, but it is widely used. TDs may be able to go over the game
  score and adjudicate the result based on the final position. If the TD
  cannot determine what happened, they may declare the game a draw or
  let the reported score stand. The worst option is for the TD to
  declare the game a double forfeit. I cannot recommend that. But
  players who get tied up in disputed resignations may want to be
  prepared for any of these TD decisions.

(This is all in the context of USCF rules, of course. Your mileage may vary under other jurisdictions.)

user17: If you keep a written record of games, the ending position can be reconstructed. Then the referee can reason from the board position whether a resignation or a draw is the more equitable result from the position.

user11609: I can't imagine making additional actions to avoid something so ridiculous. Defending against something that never happens won't help you make chess friends. The probability of this happening is 0% and the probability of this happening to you is even bigger 0%. How many times do you think player can repeat such a behavior unpunished? What sense does it make for the player? Who is going to risk his career / good name this way? People capable of that will use engine assistance in the first place. It's just half a point at risk... 

user70: In the USA, we have to notate our games. This would likely prevent issues where an opponent claimed a draw fraudulently.
I played tournament chess for years and never knew of a single instance of the sort of fraud and cheating that you mention.  (My point is that I have not had to deal with it so others may have more germane experience.)
EDIT - good observation by @ghotir.  If you agree to a result, write the result, sign the scoresheets, and do not reset the board until this has been done. Even so you both have the scoresheets.  That's how it happens at tournaments.

8209: <p>In some of the tournaments I've been to, there were pretty indecent people (some of whose licenses were revoked).</p>
<p>One of my friends had a terrible incident. At the end of the game, he was dominating and his opponent looked at him, told him that he resigned, they shook hands and reset the pieces. When the referee came, their opponent claimed that they agreed for a draw.</p>
<p>Even though the referees asked the other players, they just said they shook hands and reset the pieces together. Naturally, cameras showed the very same thing. At the end of the day, he was not able to prove the fraud and lost half a point from an already won game.</p>
<p>A similar thing might be observed at the end of <a href="https://www.youtube.com/watch?v=vxc5ZqSQ9C8" rel="nofollow noreferrer">Carlsen's defeat against Anand in Dubai</a>. What prevents Carlsen from claiming that they agreed to a draw?</p>
<p>Moreover, unfortunately, these types of frauds do not only occur in local tournaments. For instance, there was the game <a href="https://www.youtube.com/watch?v=FCjn7m8FPqE" rel="nofollow noreferrer">Tal vs. Adamski</a> where Tal's wife saved the day.</p>
<p>Thus, my question is somewhat two-folded. How should one resign properly, and proceed when the opponent tells that they resign?</p>
 13692: <p>1) When I resign, I usually do all of these: drop my king, say 'I resign', and stop the clocks, and offer a handshake. </p>

<p>2) When my opponent says he resigns, I will not shake hands immediately, rather, I will stop the clocks and call the arbiter. After the arbiter comes, I will ask my opponent to state his resignation to the arbiter. </p>

<p>Quod Erat Demonstrandum. </p>
 12523: <p>The real question here does not seem to be how to resign, but how to deal with cheaters. There are ways of dealing with cheaters which are not specific to chess.</p>

<p>After the fact, some might suggest a fistfight, :-) while others might suggest social shaming (i.e., making sure everybody in the club/tournament learns that the person is a cheater). You can also request not to be paired against the cheater in the future. Tournament directors are not required to accommodate your request, but they can consider it. Finally, you can file a formal complaint, although there better be evidence.</p>

<p>Before the fact, you can either be "paranoid" about it (for example, by demanding that the director witness the resignation as someone else suggested), or you can relax and assume good faith knowing that cheating is very rare (unless you play in an environment very different from what I know!). Up to you.</p>

<p>In any case, keeping score is always advisable, for a variety of reasons.</p>

<p>Back to the incident in question: the tournament director has a lot of discretion when dealing with "ambiguous resignations" (ambiguous is how they look to a TD in a "he said, she said" situation). Here's what Tim Just, editor of the USCF rulebook, had to say about it in his book, <em>Just Law</em>:</p>

<blockquote>
  <p>If an ambiguous resignation is disputed promptly enough, then the game
  can simply continue. If the unclear resignation is not discovered
  until much later, then the waters get muddy. Some TDs like to award
  one point to the player who says they won the game and a half-point to
  the player who says they drew the same game—I am not a fan of this
  method, but it is widely used. TDs may be able to go over the game
  score and adjudicate the result based on the final position. If the TD
  cannot determine what happened, they may declare the game a draw or
  let the reported score stand. The worst option is for the TD to
  declare the game a double forfeit. I cannot recommend that. But
  players who get tied up in disputed resignations may want to be
  prepared for any of these TD decisions.</p>
</blockquote>

<p>(This is all in the context of USCF rules, of course. Your mileage may vary under other jurisdictions.)</p>
 17: <p>If you keep a written record of games, the ending position can be reconstructed. Then the referee can reason from the board position whether a resignation or a draw is the more equitable result from the position.</p>
 11609: <p>I can't imagine making additional actions to avoid something so ridiculous. Defending against something that never happens won't help you make chess friends. The probability of this happening is 0% and the probability of this happening to you is even bigger 0%. How many times do you think player can repeat such a behavior unpunished? What sense does it make for the player? Who is going to risk his career / good name this way? People capable of that will use engine assistance in the first place. It's just half a point at risk... </p>
 70: <p>In the USA, we have to notate our games. This would likely prevent issues where an opponent claimed a draw fraudulently.</p>

<p>I played tournament chess for years and never knew of a single instance of the sort of fraud and cheating that you mention.  (My point is that I have not had to deal with it so others may have more germane experience.)</p>

<p>EDIT - good observation by @ghotir.  If you agree to a result, write the result, sign the scoresheets, and do not reset the board until this has been done. Even so you both have the scoresheets.  That's how it happens at tournaments.</p>
