The Cavalcade of America. Just as traditions of American character have grown up with our people, so the DuPont Company has grown with the nation to occupy an increasingly useful place in our economic life. And DuPont presents the Cavalcade of America in the belief that the stories of face and courage you will hear on these programs represent a heritage too precious to be forgotten. These are true episodes brought to light by the careful search of distinguished educators and historians prominent in the American Historical Association. Today as ever, America carries its traditions forward, driving through to new accomplishments, so well exemplified by the research of DuPont Chemists in creating better things for better living through chemistry. In every chemistry, in every walk of life, this spirit of get ahead, this desire for constant improvement has always inspired and will continue to inspire the Cavalcade of America. We set our stage tonight for the year 1889 with some melodies that were popular in the gay 90s played by the Cavalcade Orchestra. Our trade is more American than the spirit of healthy competition. Friendly rivalry has done much to advance our nation's progress. In every walk of life, we find the urge to succeed, to advance, to conquer difficulties and oppositions, often spurs us to win where praise softens and brings self-satisfaction. Our nation's history has many examples of contests out of which came advancement and improvement. Tonight, we are concerned with but two. In 1889, the plows of empire are leading westward. New territories are opening. Broader horizons are stretching before an eager nation. In her sister's home, Mrs. Molly Nesbeth is reading a recent copy of a St. Louis paper. Anna, Charles, look here. What is it? Somebody dead. It's the president. President Hollick. Yes? No, no, of course not. He needed a proclamation. Oh, is that all? From the way you acted, I saw a heavy... Indian territories could be opened up at last. Made part of the, what do you call it, the public domain. I saw something about that a few weeks ago on the paper. Now speak of it. And you never told me. Well, Congress ratified so many bills. Two million acres of land could be given away. I don't know why anybody would want to take up land and wilderness like that. And why? For a home, of course. For a living. A fresh start. No, I suppose there are folks, but thousands of them. Land hungry folks who've been waiting here for the chance. John always said it would come. That it was bound to come. If only he could have lived to see it. But at last it hasn't. The government brought the land from the Indians. It's to be open for settlements. One hundred and sixty acres to a person. I know the very spot I'll claim. You will claim? Yes. What are you talking about? I'm going to join the run and stake a home stand. Well, I'll let you, Molly. I've been waiting for this day for years. The day when I could get land, land of my own, for myself and my children. You've got a home here with Anna and me as long as you live, Molly. You know that. I know. And I don't want you to think I'm ungrateful. But a home of my own is what I want. And here's a chance to give it. Well, now, Molly, we'll see. We'll just think it over a while. There's no time to lose in thinking it over. The President's proclamation was issued three days ago. The land will be open in less than a month. Hundreds of folks around the road already, most likely. On the road, heading for the line. You mean you have to go there? Of course. I just suppose. I thought you sent in an application or something. You don't ask for a section of land. You go and stake it out. If you can get it. If you can get it. Yes. Two million acres. And 50,000 folks may be after it. More likely, 100,000. Then what chance have you got? Everybody's got an even chance. They aren't letting anyone across the line beforehand. Not a day or an hour, not even a minute. A lot of them are flipping ahead of time just the same. They'll be disqualified if they do. They're still right here in the paper. Well, will everybody line up at the border? And wait for the hour. Yes. The signal to start. It'll be a race. Every man for himself. Molliness. If you don't really mean you're going to join that race.  Consisting the world. Because I know just the place down always hope to stake out for us someday. You're following the whole greatest claim. There's a grove of cottonwood and a little creek. And some rolling hills. Oh, I could hit rice forest. On foot ice foes. Or on horseback. Or in a wagon. I'll find some way. Over the country they came. 100,000 people in trains, in wagons, in buggies. On horseback and on mulebacks. In ox carts and in prairie swimmers. On foot even. A crazy, heterogeneous procession. Pushing, scrambling, cursing, laughing. Eager to get to the line. Once there they waited. For they, some of them, under a burning sun. A mid-choking red dust. No place to rest. Nothing much to eat. Even less to drink. Waiting for the hour when the land would be open. In the midst of this mad milling crowd was Molly Neveson. It's back, everybody. Well, well, well, well, well, well, quiet boy, quiet. You making the run, ma'am, or just watching? I'm going in. With your husband? No, alone. You've got nerve. I got a good horse. You're right. You can't beat an Indian pony for endurance and over rough ground. Now, that fellow over yonder with a black mare, he won't be in it with you and me. No. At the race track horse he's got. Oh. Trained for short spurts. Watermelons! Where is he? Watermelons! A farmer with a whole-car load of them by a guy. Yeah, and they're going fast. Come on, let's try and get one. Oh, I don't dare to leave. I saw them all night to keep this place right in front. Well, you stay here and I'll go there. Get in there, Jerry. Well, what the place is there? You can't put your team in here. This is my place. Yeah, your place is back home, lady. Tending to your knitting. Well, this runs open to all comers, isn't it? I've got guests as much right here as anybody. Well, I hope you're a good rider. I am. Because if you ain't, there's no telling.  Trample on you. You ever seen the cattle stampede? Yes. Well, it's going to be ten times worse. Because they're not running blind all after something. Well, they're human beings, though. Yo, this noise sounds human to you. They've heard a wild animal to tell you to tend up, raring to go.  I'm not asking any favors or given any. This is my place, here in the line. That's the living boat. Got one. I got one. I got a piece of watermelon anyway. Oh. That's paid a dollar for it. Yeah. Kind of warm, I'm afraid. Excuse me. Here, take that. Oh, I couldn't die. Come on. Oh, no. There's only enough for one. You eat it. Say, what do you take me for anyway?  Here, take half. Oh. Thank you. Get the spot, don't it? Mmm. You know, I could bury my whole face in it. My eyes. Yeah. My eyes, Mark, too, like fury. It's all that brush smoke where they've burned the area ahead of us. Yeah, they did it to clear the way for us, I suppose.  What? The Sooners. The sellers who thought they'd sneak in sooner, ahead of time, and hide in the shrubs. Oh. That summer's managed to get in. Not their claims all staked up, but now most likely. Oh, but there's a panel there. Sure. Oh, there'll be plenty of arguments and shooting and lawsuits. Okay. Say, you see that fellow yonder in the spring wagon? Yeah. He's a lawyer. He's getting in on the ground floor. Oh, then they're not all going in for land. Oh. Some are making for the town site. Merchants. Builders. Bloomkeepers. Go on! Go on! A jackrabbit just run out across the line. Calling him a Sooner. Good things up to make him laugh and relieve the strain. Yeah. Back in for his body. Keeps back. Only a few minutes to go out. Yeah, you better mount your pony, man. Be ready. All right. The militias all got their watches out and their guns. Ready to give the signal. Well, how can we ever hear over all this noise? What? Wait, there isn't any noise. Have I gone deaf all of a sudden? They're listening for the signal. It's almost noon. Yeah. Oh, boy. Oh, goodness. Competition and civilization. Rivalry and progress. This spirit has always been strong in the heart of the American people. It stains the country from a wilderness to a land of hope. Even before the Oklahoma land rights, the roots of American love of competition led back to an incident which caused excitement throughout the civilized world. Our cavalcade orchestra takes up the Mississippi and the days of 1870 with an excerpt from Freddie Ghost's phase, Mississippi Suite. 1870. Down the brown waters of the Mississippi steams the Robert E. Lee, loaded with cotton for New Orleans. Captain John W. Cannon, owner and commander of the mighty packers, stands on a hurricane deck talking with one of his passengers. What's the truth, Garwin? Be there in about 20 minutes, you know. Making good time this trip, Captain. The Robert E. Lee needs good time every trip. He's in the boat on the river, can be there. Ha, ha! Now you talk just like Captain Leathers of the Natchez. Leathers? That wind there. This is a loud, mild breath. Yeah, now, Captain, what you say, Captain? Tom Leathers happens to be a good friend of mine. Well, I mean, he's both in one of those boats. Well, I did come up on the Natchez. You happen to be a good friend of mine, too. So I reckon I'll travel back on the lease. Well, uh... What do you think of the Natchez, then? A beautiful boat. Pretty as lines, I think I ever saw. Handsome ears as a handsome dog. Ha, ha! Well, the Natchez can do plenty. Leathers slave, she's the fastest boat on the Mississippi. And I don't know if...  The Robert E. Lee's got them all. Ha, ha, ha! I'm sad we have come to Natchez now. How do you know it, sir? I think I don't recognize that whistle. She was still in Vicksburg loading when we pulled out. You must have done some mighty fast traveling over Taken. Well, we've made a lot of stops this trip. Yes, she comes round the bend. You're right. It is the Natchez. Pretty as the name. Even alone there. As quiet and graceful as a... A bride, a bride. Ha, ha, ha! Hey, Sam. Hey! Go below and tell Charlie to speed up on this. Don't worry, ma'am. You haven't got a little boat. We're not going to do any racing, ma'am. Well, you see, we just wanted to get out of the way of the Natchez. He, uh, he's gaining on us, Captain. Lasted why don't Charlie pile on the wood and speed her up? He's pulling up on us, sir. Don't let her pass us, Captain. No, you mustn't let her pass us. Well, I thought you was the one who just said that. I know, but, uh, well, it's all right with me if you speed up a little. I can't bear to see that other boat getting ahead of us. Fine. Please, Captain. Charlie says he's making all the speed you can, sir, with a few of us. Tom Neaton. Well, we're taking on more of that route, sir. That route? I want it now. Oh, sorry, sir, but we're doing the best we can. All right, all right. That's a little effort. Well, you can't hardly blame him for wanting to show up with a brand-new beautiful boat. Boy, he's done it with every boat he ever had. Way back in 1955, when he had the first Natchez, I had the old leaf. He could save a trick of his. Sneaking up and then swooping back. I'm almost the rest of our stern. Pass it. He's pulling right up alongside it now. Look at the way he cuts the water. And don't let him do this, sir. Well, we're going as fast as we can, ma'am. Look at him as he goes fast, Captain. Waving at you? From the old pool. I'll show him. I'll show him who's got the best boat. Challenge him to a race. And prove who's got the best boat. Challenge old leather to a race. A race what is a race. All the way up the river from New Orleans to St. Louis. 1200 miles. And then we'll see which is the fastest boat on the Mississippi than Natchez or the Robert E. Lee. From this challenge came the race which attracted nationwide, worldwide interest. The race between the Natchez and the Robert E. Lee. Enormous sums were wagered. Not only in the river cities, but in large cities all over the United States, Canada, Mexico, Great Britain, and Europe. Late afternoon, June 30th, 1870. The levee at New Orleans is strong with people eagerly awaiting the start. Well, I went down in New Orleans by my wife's phone machine to load a heap of bags. So I'm the Natchez on ease I'm begging on the lease. $500? Natchez will be there. Don't. Bravo what I mean. Back to the boat that bears the honor name of our general. Back to the boat with the best machinery, say I.  She's bigger. She looks bigger because she's wider and rises higher out of the water. But actually, she's not as big. Her name goes to take it from the world. You southerners are always loyal. They're about to start. Look, Lily is backing out. Oh, what would I give to be a boss? No, not for love or money, could you or anybody else get past the gunner? That thing cannot refuse positively to take any passengers of cargo. Naturally. It makes the room for fuel. What's the battling, wood or coal? Boss understands. He's got a big supply of things on hand for vector speed, rosin, pitch, hello, candle. He makes me. The levee looks as if a cyclone had struck her. Even her wheelhouse is ruined. Captain Salmon has made thorough preparations. That Captain Leveres has made practically none. He's even carrying a cargo in passengers. And still, he wins. Another 500 on the Robert E. Lee. Bacon. They've slung it to the... out! There it is! Johnny Hawkins' famous saloon. On the corner of Common Street and Riot is Halley, New Orleans, hundreds waited all night for news. 34 miles quick. Ahead by 4 minutes and 40 seconds. He will hold the lead long once old Leveres begins to let the Natchez out. And again for bad news! A good morning, July 1st in a Creole Hall. Which one you bet on, Miss Luzes? The Natchez, Mander. Why Miss Luzes? I know. But the Natchez was the boatman for John and I took our honeymoon tip on. No, the associate warden is Luzes. And you're betting on the Robert E. Lee, Mander? I would guess that. He's not on the lead, isn't he? He's joyous, ma'am. And that good-for-nothing doggie tells me... Luzes, Luzes! Yes, Sam, what is... Just put a bulletin' up down at the square. The Robert E. Lee breaks all records to the town Natchez. 17 hours and 11 minutes. No! I know York's not an exchange house on the morning of July 2nd. What's the latest on the board, Frank? Well, it's consolidated. The old news paper consolidated. Who's ahead in the race? The Robert E. Lee, sir. He passed Memphis, sir. 10 minutes past 11. All business has been suspended to the day. I told you the Lee would win. Don't be too sure. The race isn't half over yet. The Lee's gaining all the time, though. She'll win by an hour. She's got an unfair advantage. Having attended a fueler in midstream. She's got a smart cap. $1,000 at the Natchez will reach St. Louis first. Take it. Who saved London Club July 1st? What's the latest table report, Briggs? They passed Cairo, sir. Cairo? Not Cairo on the Nile, sir. Cairo on the Mississippi. Oh, right. Extraordinary, isn't it, sir? A race that runs for days on end. Most extraordinary, Briggs. Just why are they doing it, sir? Well, Americans are always racing and competing. But why, sir? Why, that's not all, Briggs. I don't know. But I do know I've got 10 pounds wages on the Natchez. Yes, sir. And I have 10 pounds on the Robert E. Lee. St. Louis. Shortly before noon, July 4th, 1870. For miles, both banks of the river are crowded with people. The hills are swarming with them, waiting to welcome the winner, whichever it may be. As you come, I can see it. It's the Natchez. Natchez, you're grander. Why, it's the Lee. You can tell by the way she rides. I don't see how you can tell anything, though. Those stairs go in the way. Oh, I've seen the Lee too many times, unless you can't pull me. I sure it's the Lee. The Natchez is way behind. But he was packing up the Natchez. And $25 of my money says it's the Lee. Take it, strangers. Oh, I can't believe it. No three days, a long time for race. Yes, sir. Hey, that's her whistle. Yes, sir. Only one on the river like it. The Natchez. No, no, the Lee. Come on, Captain Cannon. We're waiting for you. It's the Lee, all right. It is, sir. It's fancy. I'm sorry to disappoint you, miss, but I don't know the Lee's whistle anywhere. Yes, it's the Lee. I can read her name now. I saw the General Robert E. Lee's there, friend. I'll tell him it's that $25, friend. Yeah. We'll... Three tears for the Robert... From New Orleans to St. Louis in three days, 18 hours and 14 minutes. That was the record of the Robert E. Lee. Racing became more than a mere contest between rival captains. Racing was responsible for the improvement of the Mississippi Steamboat. Racing, rivalry, the spirit of competition brought better travel conditions, faster transportation of merchandise, progress and advancement. The Oklahoma Land Race was instrumental in conquering a wilderness. Let us be thankful that this inherent quality remains an essential element in our country's lifeblood, for the spirit of progress helps make America a nation. The other night I found out again that the American determination to strive and succeed is very much alive today. I wish that all of you could have sat with me at a dinner table, where I met a number of men whose daily work consists of the hardest sort of competition, competing with nature, using their brains and ingenuity to go nature one better. They were all research chemists. As they swapped experiences across the table, I was amazed to learn how far into the future their thinking extends and also how close they were to discovering new secrets of nature that will change and improve our lives tomorrow or next week or a year from now. One of those men told me the story of the part salt plays in chemistry. Well, you know, I had the slightest notion of the number of useful things that DuPont makes for us out of salt. Common salt. I thought salt was just something you put on french-fried potatoes and something that makes it easy to swim in the ocean. But these chemists told me they take salt as a basic raw material and make things as far apart as insecticides for farmers and cosmetics for beautiful women. Every time I pick up a salt shaker now, I remember that DuPont uses that same material to make products used in ethyl fluid for gasoline and Duprene, the marvelous synthetic rubber that beats nature's own rubber in many ways, even adhesive, cleaning fluid and ingredients for dentifers all out of the stuff I throw over my left shoulder for luck. And salt is lucky after all. We're lucky to have it around and we're lucky to have chemists who know what to do with it, how to turn it into many useful products. Another time, I'll tell you more of these fascinating adventures in the chemist's constant effort to provide better things for better living through chemistry. Next Wednesday evening at this same time, Frank Craven, well-known playwright, director and popular star of stage and screen, will be our guest star when DuPont presents The Cavalcade of America. This is the Columbia Broadcasting System.


Hello, my name is Christian Mayans, and this video talk is about the paper Quantum Secure Message to Authentication via Blind Unfortability. This is joint work with Corinne Allergitsch, Alexander Russell, and Fangsong. Let me start with a short introduction. On this painting, you see a woman who is receiving a letter, so we can imagine two security-related thoughts going through her head right now. The first one is, okay, on the bottom of the letter, it says, sincerely, X. But how can I know that this letter is really from X? Anybody could have written that there. And the second one is, okay, this courier looks really sketchy. And probably, he has been on the road for five days or something. So anything could have happened to this letter in between extending it and me receiving it. Nowadays, we can reassure the recipient of a message with regards to both of these concerns by the use of digital signature schemes and message authentication codes. In the remainder of this talk, I will focus on message authentication codes for simplicity of exposition, while all the security notions, etc., apply to both of these kinds of schemes. How does the message authentication code work? So let's assume Alice wants to send a message to Bob. And to authenticate it, she shares a secret key K with Bob. She begins by computing the so-called MAC tag using the MAC function, her secret P and the message. Then she sends the message together with the tag to Bob. Upon receiving a message tag pair, Bob uses the message and his copy of the secret key to recompute the tag. And if it doesn't match the one he received, he rejects. Otherwise, he accepts. The security property that we want from such a MAC is called unfortability under chosen message attack or UFCMA. Works as follows. We consider a message authentication code secure if no forgery adversary can be successful in the following game. This game, the adversary gets Oracle access to the MAC function, can make a number of queries. So send messages to the Oracle and receive tags back. And in the end, the adversary has to submit a message tag pair, mstar, tstar. And he wins the game if this is a valid message tag pair and if it's distinct from all the queries he made to the Oracle. In this paper, we study quantum access security of MACs. So that means that instead of providing a classical Oracle for the secret key MAC function, we provide a quantum Oracle for it to the adversary. That means we give Oracle access to the functionality defined here. And one obvious question that one might ask is, why would we consider such a setting? There's a couple of answers to it. First of all, one answer is because we can. So as theoretical cryptographers, we are often interested in as strong as possible security and this turns out to be possible. Second, there's also a motivation from post-quantum composability. So for example, if we use an obfuscation to publish an obfuscated circuit for the secret key function, then of course, a quantum attacker can implement it on their quantum computer and evaluate it in superposition. Finally, a third reason might be physics. So this is maybe a bit less likely to actually realize this risk. But if you imagine, for example, a smart card that has a secret key hardcoded in it, then one might imagine an attacker that freezes this smart card, cools it down to near absolute zero temperature and hopes that it starts to behave in a quantum way. So first of all, let's try kind of the naive generalization of UFCMA. So let's call that unforgibility under quantum chosen message attack. So here's an example attacker. This attacker just prepares a uniform superposition of messages uses the oracle to convert it into a uniform superposition of message tag pairs and afterwards applies a measurement to obtain a random message tag pair and outputs that. So two thoughts about this. First of all, clearly this should not be counted as a break of the scheme because it's clearly possible for any Mac and it's in some sense just a quantum analog of the algorithm that samples a random message queries it and then outputs that the resulting message tag pair. On the other hand, it turns out that the output is almost distinct from the query, right? So it's almost orthogonal to the query. So therefore somehow UFCMA doesn't seem to make sense anymore. Okay, so we cannot generalize UFCMA in a straightforward manner, but then how can we judge whether a function is unpredictable for quantum algorithms? How do we identify a successful forging adversary? We've just seen a non-example, so an example of an attack that we shouldn't count as successful. Here's one that we that we should be worried about. Let's specify a Mac by choosing a random periodic function with period pk, but then puncturing it at the input pk and set the output to zero there. So now there's the following adversary. We first start by running the so-called period finding algorithm, which is a subroutine of Shor's algorithm to find the period pk and afterwards we just output the pair pk, zero. This clearly should be counted as a successful attack because we have kind of planted this vulnerability there and this is not the analog of a classical attack that also should work. Here are some additional problems that arise when generalizing UFCMA to the quantum pigs. First of all, there's the so-called no-cloning principle that says that a quantum state cannot be copied. This implies that we can't even think about the straightforward generalization in the sense that we cannot compare the output of an adversary to their queries and in addition, if we were to find a way to compare the output with certain messages, then such a comparison would most certainly involve quantum measurement, which changes the state that is being measured. So then we could only do at most one such comparison. Let me move on to our results. Here's an overview. As I said, we study unforgeability under quantum chosen message attacks. In this setting, we propose a new security definition, which we call blind unforgeability. The motivation for proposing a new definition is that the previously proposed definition by Bonet and Jandri from a Eureka paper from 2013 is insufficient to capture all possible quantum attacks. So this has been suspected before and we confirm this by exhibiting a MAC that is secure under this previous definition, but on the one hand, intuitively broken and on the other hand also insecure under our new definition. We go on to characterize blind unforgeability by first proving that it also implies the previous definition by Bonet and Jandri, but also by proving that random functions on the one hand and also the lamp or at one time signature scheme are secure under it. Finally, we also prove that the so-called hash and MAC or hash and sign paradigm preserves BU security if we choose an appropriate hash function. Let us quickly recall the previous security definition by Bonet and Jandri. So their approach was as follows. They just say, okay, fine, we cannot compare a forgery with the query transcript. So let's just ask a little bit more from the adversary. Let's just ask them to output Q plus 1 valid message tag pairs. So in that sense, if they make Q queries and output Q plus 1 message tag pairs, one of them has to be fresh. This has a couple of nice properties. For example, it's equivalent to UFCMA in the classical setting and also a random function or a random oracle is busy, unfortable. So already before our work, there were some doubts in the literature about whether this is the correct definition of security. This was mainly suspected in a paper by Garg Ewen and Jandri and later also elaborated on in the quantum lightning paper by Jandri. So here are the problems. So first of all, say an adversary can make a genuine forgery for a Mac, but to do that, the adversary has to make a number of queries and then completely measure the whole state and thereby destroy it, right? Then they can maybe output the final forgery, but not a number of queries, many other valid message tag pairs. In addition, maybe such an adversary can make a number of queries inside a certain region of the message space and then make a forgery outside of that reason. So no matter whether we can compare, et cetera, this should really clearly count as a forgery, right? In fact, just looking at these options, it should be easy to come up with an example where this happens. Turns out that that is not that easy, however. And one of the reasons is that, for example, this period finding attacker that we talked about doesn't work to show this. And this is because if a quantum measurement succeeds with good probability, then the disturbance is also limited. So in this period finding example, the adversary makes a measurement to determine the period. But afterwards, because that succeeds with good probability, they can still rewind their computation and recover a message tag pair from their query. In the quantum lightning paper, there was, in fact, constructed a MAC that is secure according to the Boney-Jandry definition, but insecure according to a one-time security definition put forward by Garg, UN, and Jandry. But this was assuming in distinguishability obfuscation. And I don't think one can call it an intuitive example. This brings me to our first contribution. We construct a MAC that kind of unconditionally breaks the Boney-Jandry definition. Here it is. The message space are the N plus one bit strings. The first bit we call B and the rest is X. And the output has two parts, which are both functions of X determined by B. So for B equals zero, the first part is a random periodic function with period P. And the second part is a uniformly random function. But if B equals one, then the first part is a uniformly random function except if the input is P, then we set it to the all zero string. And the second part is just identically zero. This is kind of complicated. But in summary, the message space is split into two parts determined by the first bit. And if that first bit is zero, then we have a random periodic function, but it's kind of shielded by another random function. Whereas if B equals one, then we have a random function that's punctured at that same period as an input. There's a simple one-query convincing forgery attack. Works as follows. First, use the period finding algorithm to find the period P. And this is done by ignoring the uniformly random part of the output. And then just output the message one P together with the all zero tag. This is a convincing forgery because the period finding algorithm uses a uniform superposition of the messages that start with zero, while the forgery is on a message that starts with one. In addition, we can prove that there's in fact no efficient quantum algorithm that wins the boney-jandry security game for this map. This is kind of difficult to prove, it turns out. And a key step is to show that if an attacker wants to learn anything about the period P, then kind of this ignorance of the random part of the output is necessary. So after giving this convincing counter example, we have moved on to proposing a replacement definition, which we call blind affordability. So how does it work? The idea is as follows. So instead of providing an adversary with a proper oracle for the MAC function, we provide them with a modified oracle that is kind of blinded in a certain random subset of the inputs. Afterwards, we ask the adversary to afford in one of the blinded spots. More formally, we define a set B epsilon, which is a random subset of the message space. And each message is put into the set with independent probability epsilon. Now we define the blinded MAC oracle by sending every message to its corresponding tag, if the message is not in the blinding set, but by returning the bottom symbol if the message is in the blinding set. The definition is now as follows. A message authentication code is called blindunforgible if no adversary can output a valid message tag pair with the message being in the blinding set when provided with the blinded oracle. So great, we have come up with a can as a replacement. Let's check whether it actually works. So first of all, we can prove that it's equivalent to UFCMA if we restrict to a classical oracle. So that's reassuring. Also, we can prove that a random oracle is blindunforgible. The other standard is sent into check. We also prove that it implies the previous definition, which builds additional confidence. And finally, it classifies all the examples that we know correctly. So here's the first example that we looked at, the kind of the stupid forgery adversary that shouldn't be credited with breaking. Let's see whether it succeeds in the blinding forgibility game. We could, for example, consider this for a random function. If we now consider a blinded oracle, then the output of the random oracle for a blinded input is independent of any adversarial state. So this adversary clearly has to fail. Now let's look at our constructed MAC that we've used to show the insufficiency of the Boney-Jandry definition. So here, let's just take a very small value of this epsilon. That means that the oracle is almost the correct one. And the period is a global property of the MAC. So the period finding algorithm would still almost succeed with the same probability as if the adversary was provided with the correct oracle. The forgery message, on the other hand, which is completely separate from the query that the adversary makes, is blinded with independent probability epsilon. So this adversary, in fact, succeeds with small probability. Here are some additional results that we have about this new notion. We define a new security notion for hash functions, which we call Bernoulli preserving. This generalizes collision resistance to the quantum setting, and it strengthens the previously proposed notion of collapsingness. Using a hash function that is Bernoulli preserving, we can prove that the so-called hash and MAC paradigm is blind and affordable. Furthermore, we construct such a Bernoulli preserving hash function by proving that a contraction by Unruh based on LWE is actually, here are a number of additional results that we have about our new security notion. We define a new, here are a number of additional results. We define a new security property for hash functions, which we call Bernoulli preserving. This property generalizes collision resistance to the quantum setting, and it strengthens a previous such generalization, which is called collapsingness. Using this notion, we can show that hash and MAC instantiated with such a hash function is blind and affordable, and we can also show that a construction of a collapsing hash function by Unruh that's based on the LWE assumption is actually even Bernoulli preserving. In addition, we can show that lamport signatures are one time blind and affordable if they are instantiated with a random oracle. To prove these results, we use mainly two tools. First of all, we have a simulation lemma that shows that an attacker doesn't behave very different if provided with a blinded oracle with small blinding parameter compared to an unblinded oracle. As a second tool, we use the superposition representation of a random oracle by Gendry. This we use extensively, so both for the proof of Bernoulli-Gendry security of the separation example, as well as for the implication blind and affordability implies Bernoulli-Gendry affordability, and for the security proof of the lamport signature scheme, we all employ the superposition representation of random oracles. This brings me to my last slide. Here's the summary and some open questions. As we have seen, there is a MAC that is secure according to the previous definition by Bonnet and Gendry, but allows for an intuitive forgery attack. So this definition really needs to be replaced, and we have such a replacement, which is called blind and affordability. Blind and affordability has a lot of nice properties and classifies all the known examples that we have correctly. Here are some open questions. First of all, the security gain for blind and affordability is not very natural. This is because the adversary is provided with this blinded oracle, which is kind of different from the actual functionality that we're testing. One question is whether this can be fixed somehow. And another open question is, are popular schemes blind and affordable? So what we know is that the lamport one-time signature scheme, as well as some pseudo-random function-based MACs are secure, but these are the only examples for now. Thank you very much.


My name is Richard Varela. I'm the Park Director at Hornlake Caves Provincial Park. For the last 24 years, it's been my job to take people and show them the magic of the underground world. My name is Drew Chatlin. I'm a park ranger with BC Parks. I've been with BC Parks for nearly 30 years, and Hornlake Caves is one of the parks that I manage. Through my work with BC Parks in the last 30 years, I've been responsible for ensuring public safety and the protection of the natural and cultural features for the public to come and enjoy and to learn from. There are over 1,500 caves on Vancouver Island, and they form in a karst landscape. A karst landscape is essentially bedded in limestone or a water-soluble rock. This limestone was created on the floor of an ancient sea from the coral reefs and shellfish deposited there millions of years ago. Over time, water will travel through the cracks in the limestone and those cracks will open up into the caves that we can see today. Speleothems are the beautiful crystals that grow inside of caves after the caverns have been formed. This dripping water leaves behind tiny microscopic particles with every droplet, making the stalactites microscopically longer. Over thousands of years, they'll form stalactites, stalagmites, brain rock, moon milk, flowstone, many different kinds of features that are all made out of the same material. It's calcium being re-deposited in the cave by the water, and the calcium has come out of the limestone, which originally was the shells and the coral reefs from an ancient sea. Caves and karst are important parts of the British Columbia landscape. Caves play a vital role in clean water and healthy forests. Caves and karst are also important for scientific values. Caves contain seed and pollen data that you'll find in the sediments built up inside the cave. Also, you can get climate data from the speleothems. Caves are also wonderful repositories for bone beds and fossil records that are archaeological and paleontological evidence of previous historical data. One of the things that, when you're a park there, one of the things to remember is to always, you know, respect the environment around you. Make sure you wear good sturdy footwear. Rocks are very slippery and they're wet.  Make sure you've got lights. You have spare batteries. Remember, dress warmly because the caves are cold and damp. The temperatures are usually around 8 degrees or 50 degrees Fahrenheit. When you head out into a cave or into any back country area, make sure you let somebody responsible know where you're going and also to let them know what time you're going to be home. The limestone here in this park was formed over 250 million years ago, so you can imagine how long it's taken for these features to become present for you to enjoy. So we just ask that you show that a little bit of respect when you're here. Whenever you go inside a cave, it's important that you don't touch the crystal formations. They're very delicate and take thousands of years to grow. Simply touching them will deposit the natural oils on your skin on these crystal formations and inhibit their future growth. You can kill these formations by simply touching them. The park offers something for everybody. All ages and abilities. From easy family cavern tours to wild underground adventure. Helmets and lights are available if you would like to self explore these caverns or you can enjoy an educational guided tour. These tours leave every hour on the hour from 10 a.m. to 5 p.m. 7 days a week. Aside from caving, there are many other activities that park visitors can enjoy. Park visitors who choose not to enter the caves can also learn more about the park by going into the visitors' center, looking at the museum and the geological displays and walking the outside trails. We've had cave explorers here as young as five and all the way up into their 80s. So Horn Lake really does offer something for everybody. We invite you to come out to Horn Lake Caves Provincial Park and enjoy these underground environments.


Top 15 Mistakes on a Laser Machine Hello everyone, this is Watson, and in this video we'll tell you about the most common mistakes when working on a laser machine.  This video will be useful for both professionals and those just starting to use our laser machines. Subscribe to our channel so you don't miss any new videos. 15. Safety Hazards The most important thing when working on a laser machine is accidents prevention. Safety hazards can lead to injuries, skin and lung burns, arc eyes, damage of the machine or its components, and fire. The main things to pay attention to are grounding, fume extraction, a voltage regulator, and processing the right materials. It is not recommended to cut PVC, thick rubber, and Teflon on CO2 laser machines. As the vapors occurring during cutting, these materials are toxic. Be aware of the laser beam path and do not fall its way. The path of the beam is not visible and you need a clear understanding of the dangerous area. It's recommended to always work with a lid closed. Watson machines have protection against opening during operation. The machine stops when the lid is open. If you regularly look at the laser while it is running, you can quickly damage your eyesight. Use safety glasses. Important. Never leave a running machine unattended as most force-major events can be dealt with in the first few minutes. 14. Improper Alignment Alignment is the adjustment of the position of the mirrors to ensure the correct beam transfer from the emitter to the material. This is one of the most important aspects. Improper or misaligned alignment causes distortion in the layout. Poor cutting. Reduced power, split beam, thick or black cuts. As soon as there are any cutting problems, the first thing to do is to check the alignment. We have already prepared a detailed video on how to do the alignment. So please subscribe to the Watson Channel and the Watson Technical Channel to learn more about the maintenance of our equipment. The next point is 13. No Air Compressor An air compressor is used to cool the lens and blow the combustion products out of the cutting zone. The stronger the airflow, the cleaner the cut, and the faster the machining speed can be achieved. Without an air compressor, the combustion products get on the lens, accumulate on it. The laser beam heats up the dirt and dust on the lens, and the lens fails sooner. It overheats and breaks. The compressor not only provides blowing, but also prevents certain materials from catching fire. Monitor the operation of the compressor. 12. Operation without cooling It is impossible to work without any cooling system. If the tube overheats, microcracks occur, and the tube loses power and fails prematurely. For a more comfortable operating process, it is recommended to buy a chiller. For example, CW5000. And you will not have to think about laser tube heating too much. The chiller has a closed circuit, and the water in it is not in contact with the outside environment. However, do not forget to switch it on before you start. 11. Laser tube current is not set correctly If the current is too high, the electrodes of the laser tube overheats. The power subsides, and the tube fails after about three months. And if the current is too low, you will not use the power resource built into the tube. For more details, see one of our videos. The link is in the description below this video. 10. Wrong focal length setting Results in a loss of power, skewed edges, or an indistinct pattern. Adjustment is carried out by moving the nozzle with a focusing lens up and down. This can also be done by raising or lowering the table, if your table is equipped with a necessary mechanism. Our machines are always equipped with a piece of acrylic with the set focal length. On Watson Technical, you can find the video on how to set the correct focal length when starting the machine for the first time. 9. Over-under-tightened belts It's always better to under-tighten the belts than over-tighten them. If the belts are too tight, there is a risk of increased wear, jerky cuts in corners, creaking, and in particularly difficult cases, skipping steps. Too loose belts can cause incorrect workpiece geometry and poor engraving quality. The belts should not sag, but at the same time, you should be able to move the working head by hand without much effort. If this is difficult, loosen the belts a little. 8. Poorly fixed lens Sometimes it happens that the lens is not properly fixed when cleaning or replacing it. Then, during operation, when the laser head moves, the lens vibrates, which results in uneven cutting. 7. Wrongly prepared cutting file The most common mistakes are overlapping lines. The machine cuts the same area twice. The cutting file is divided into hundreds of segments. This can happen when exporting files from engineering programs like AutoCAD incorrectly. The machine will cut jerkily and jump from segment to segment in a chaotic order. Instead of smooth curves, there will be broken and uneven segments. Wrong Scale Remember that the scale should be one to one. 6. Unoptimized cutting process Optimization of the cutting process determines which lines and in what sequence the machine will cut. If you want to cut a pattern inside a circle, you must first cut the pattern and then the circle. If you do not adjust the optimization and cut the circle first, it will fall off and the cuts inside will not match. Also, sometimes some tasks take hours to process. Although with proper optimization, the processing time can be reduced by several times. 5. Wrong parameters in the control system These are power, speed, acceleration, and step width when engraving. Wrong parameters can lead to rejects. CO2 laser operators often neglect the so-called angular or minimum power. When a particular cutting speed is set, the machine moves at a changing speed and has both accelerations and decelerations at corners and turns. If the power is constant, the laser will burn the material at the points where the movement changes. To prevent this from happening, it is necessary to set the minimum or so-called angular power, which will change in proportion to the speed. 4. Working on materials Without a pre-test, you have to allow for sample and reject material, which is about 10-15% of the total volume. There might be knots in plywood or an operator's mistake when the material is accidentally shifted. In both cases, the product will be ruined. Now, let's talk about the top three mistakes. 3. No machine maintenance Dust and dirt are electrically conductive, so if there is a small contact breakdown somewhere, that means electricity dissipates through that dust and dirt.  Also, dust can cause short circuits or overheating of the equipment. Wiping down the lens at the end of your working day will prolong its service life and reduce the number of rejects. 2. Docking point set incorrectly Sometimes owners of CO2 laser machines click all the checkboxes without reading the instructions and not understanding how the program works. The Watson CO2 laser machines have a special function called docking point. This is the position to which the machine moves after the layout is finished. This is convenient for changing material after the current job is completed. If this position is set outside of the work table coordinates, when the layout is complete, the laser head will try to arrive there, ignoring the end sensors and work table dimensions. 1. Machine does not turn on The most common malfunction is due to operator inattention. 1. Power supply not switched on 2. Machine lid open 3. Unlocked key 4. Disconnected USB cable and others These seemingly obvious points are often confusing to inexperienced users. Be careful and cautious when working with machines. Read the instructions and follow the recommendations. Write in the comments what errors you have encountered. Please like this video if it is useful. See you in the next video. Bye!