... attack2.1
Not to be confused with what is usually called a Trojan horse attack in computer security. 
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... concave3.1
Sometimes convex is called convex-$ \cup$ and concave is called convex-$ \cap$. 
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... bits4.1
Note that if the only channel available can only transmit bits, the value must be rounded up to the nearest whole bit. 
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... l'Hospital's4.2
L'Hospital is nowadays often spelled l'Hôpital. 
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... cards4.3
This was published in 1948. Information storage has evolved quite a bit since. 
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...tag5.1
Often called Message Authentication Code, MAC. 
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... Bob5.2
In the case of digital signatures, Bob can validate the tag but he can not compute it before he has seen it. With symmetrical message authentication Bob can both calculate and validate the tag. 
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....5.3
Many other functions than XOR will also work, but XOR is normally used in examples. 
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... families5.4
They are sometimes called classes or sets instead of families. 
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... degree5.5
Polynomials of higher degree are also possible and usable. When allowing all polynomials of degree less than $ n$ a strongly universal$ _n$ family is created. 
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