add README

README.md

+Write a program in Java that is capable of the following:
+
+1. One can generate an RSA key pair of realistic size. Therefore, the following steps are
+necessary:
+
+(a) Two different primes are created and multiplied using the class BigInteger.
+(b) A suitable e is chosen and the corresponding d is computed. In particular, you have
+to implement the Extended Euclidean Algorithm.
+(c) The private key is stored in a file sk.txt in the form (n, d) with n and d in decimal
+representation. The public key is stored in a file pk.txt in the form (n, e).
+
+2. One can read in a text file (ASCII) text.txt into a string and encrypt this string in the
+following way:
+
+(a) One reads in a public key from a file pk.txt.
+(b) Every character of text.txt is converted to its ASCII code (number between 0 and
+127).
+(c) Every such number is encrypted with the RSA scheme. In particular, you have to
+implement the fast exponentiation algorithm.
+(d) The encryptions are stored in a file cipher.txt (in decimal representation and separated
+by a comma).
+
+Remark: This character by character encryption is not secure as statistical analyzes are
+possible. (The letter frequencies of the plain text coincide with those of the cipher text.)
+RSA is in practice hence not used in that way but in a clever way in combination with a
+symmetric scheme. This is part of the cryptography courses.
+
+3. One can decrypt a file cipher.txt (that has been constructed in the way described above)
+with a private key in sk.txt and store the resulting plain text in text-d.txt.
+
+4. Decrypt the file cipher.txt with the secret key in sk.txt.
+
+General notes:
+
+1. You can work in groups of at most 3 people.
+2. A complete solution yields a bonus of 0.3 on the grade of the first assessment. (The final
+continuous assessment grade is, for technical reasons, between 1.0 and 6.0.)
+3. The program should be comprehensibly commented.
+4. I assume that, for fairness reasons, you do not try to cheat. However I will check this also
+with tools. If I detect an attempt to deceive by submitting (disguised) copies of parts of
+existing programs, taken from the Internet or fellow students, I will set the grade of the
+next assessment to 1.0.
+
+
+Submission deadline: 27.3.2017, 10:00 a.m.
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