羊皮传书 古希腊的斯巴达人将一条1厘米宽、20厘米 左右长的羊皮带,以螺旋状绕在一根特定 粗细的木棍上 復大辱软件学院 LiJT
LiJT 6 羊皮传书 • 古希腊的斯巴达人将一条1厘米宽、20厘米 左右长的羊皮带，以螺旋状绕在一根特定 粗细的木棍上
藏头诗 明才子唐伯虎: 我爱兰江水悠悠,爱晚亭上枫叶稠。 秋月溶溶照佛寺,香烟袅袅绕经楼。 明朝解缙祝某宰相寿辰进诗: 真真宰相,老老元臣,鸟纱戴顶龟鹤遐林 粗看"密文”,浑然诗句颂扬兼祝愿,福禄寿全有; 细究则密语藏头挖苦带讽刺,诅咒"真老乌龟” 復大辱软件学院 LiJT
LiJT 7 藏头诗 明才子唐伯虎： • 我爱兰江水悠悠，爱晚亭上枫叶稠。 • 秋月溶溶照佛寺，香烟袅袅绕经楼。 明朝解缙祝某宰相寿辰进诗 ： • 真真宰相,老老元臣,乌纱戴顶,龟鹤遐林. – 粗看"密文” ,浑然诗句,颂扬兼祝愿,福禄寿全有; 细究则密语藏头,挖苦带讽刺,诅咒"真老乌龟
Caesar Cipher earliest known substitution cipher by Julius caesar first attested use in military affairs example meet me after the toga party PHHW PH DIWHU WKH WRUD SDUWB 復大辱软件学院 LiJT
LiJT 8 Caesar Cipher • earliest known substitution cipher by Julius Caesar • first attested use in military affairs • example: meet me after the toga party PHHW PH DIWHU WKH WRJD SDUWB
ef, Caesar Cipher Exercise we are students of fudan uni versity Encrypt? zh duh vwxghgwy ri ixgdq xq l yuv I wb 復大辱软件学院 LiJT
LiJT 9 Caesar Cipher Exercise we are students of fudan university zh duh vwxghqwv ri ixgdq xqlyhuvlwb Encrypt?
Terminologies laintext- the original message ciphertext- the coded message key -info used in cipher known only to sender/receiver encipher (encrypt)-converting plaintext to ciphertext decipher(decrypt)-recovering plaintext from ciphertext cipher-algorithm for transforming plaintext to ciphertext 復大辱软件学院 LiST
LiJT 10 Terminologies • plaintext - the original message • ciphertext - the coded message • key - info used in cipher known only to sender/receiver • encipher (encrypt) - converting plaintext to ciphertext • decipher (decrypt) - recovering plaintext from ciphertext • cipher - algorithm for transforming plaintext to ciphertext