Encryption methods based on plaintext length

A method comprising:

• obtaining a plaintext;
• obtaining a key from a plurality of keys;
• determining, by an encryption selector, whether the plaintext is longer than a predefined threshold length;
• based on a determination by the encryption selector that the plaintext is longer than the predefined threshold length, encrypting, by a first encryptor, the plaintext with the key to generate a first ciphertext having a length of the plaintext, wherein the first ciphertext comprises, at a predefined position, a character from a first subset of characters wherein the character from the first subset of characters indicates a first encryption method was used to produce the first ciphertext;
• and
• based on a determination by the encryption selector that the plaintext is not longer than the predefined threshold length, encrypting, by a second encryptor, the plaintext with the key to generate a second ciphertext longer than the plaintext, wherein the second ciphertext comprises, at the predefined position, a character from a second subset of characters, wherein the character from the second subset of characters indicates a second encryption method was used to produce the second ciphertext, and wherein the second subset of characters does not intersect with the first subset of characters.

A non-transitory machine-readable storage medium encoded with instructions executable by a processor of a computing device to cause the computing device to:

• obtain a ciphertext;
• based on a character positioned at a predefined position in the ciphertext, determine whether an encryption method that was used to generate the ciphertext is a length-preserving encryption method or a length-extending encryption method, wherein a character from a first subset of characters indicates that the length-preserving encryption method was used, wherein a character from a second subset of characters indicates that the length-extending encryption method was used, and wherein the first subset of characters does not intersect with the second subset of characters;
• based on the encryption method and the ciphertext, determine a key reference associated with a key that was used to generate the ciphertext;
• obtain the key based on the key reference;
• and
• based on the encryption method, decrypt the ciphertext using the key to produce a plaintext.