How to Encode and Decode Using the Vigènere Cipher

SOLVED:(a) Encipher the message HAVE A NICE TRIP using a Vigenère cipher with the keyword MATH. (b) The ciphertext BS FMX KFSGR JAPWL is known to have resulted from a Vigenère cipher whose keyword is YES. Obtain the deciphering congruences and read the message.

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Tutorial: Caesar and Vigenere Ciphers | CodeHS

Vigenere Verschlüsselung: Erklärung und Entschlüsseln