python编写的维吉尼亚密码加解密程序

维吉尼亚密码表

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#维吉尼亚密码  加密

key='helloworld'

plaintext='whereisthekey'

#key='relations'

#plaintext='tobeornottobeth'

ascii='abcdefghijklmnopqrstuvwxyz'

keylen=len(key)

ptlen=len(plaintext)

ciphertext = ''

i = 0

while i < ptlen:

    j = i % keylen

    k = ascii.index(key[j])

    m = ascii.index(plaintext[i])

    ciphertext += ascii[(m+k)%26]

    i += 1

print ciphertext

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#维吉尼亚加密算法 解密

key='helloworld'

ciphertext='dlpcsegkshrij'

#key='relations'

#ciphertext='ksmehzbblk'

ascii='abcdefghijklmnopqrstuvwxyz'

keylen=len(key)

ctlen=len(ciphertext)

plaintext = ''

i = 0

while i < ctlen:

    j = i % keylen

    k = ascii.index(key[j])

    m = ascii.index(ciphertext[i])

    if m < k:

        m += 26

    plaintext += ascii[m-k]

    i += 1

print plaintext