This is an exercise in secure symmetric-key encryption, implemented in purePython (only built-in libraries used), expanded from Bo Zhu's (http://about.bozhu.me)AES-128 implementation at https://github.com/bozhu/AES-Python

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Sep 08, 2014  The given message is encrypted with AES-128 using the AES key and IV from step 2), in CBC mode and PKCS#7 padding. A HMAC-SHA256 is generated from the concatenation of the salt from 1) and the ciphertext from 3). The final ciphertext is HMAC + salt + ciphertext. Dec 23, 2019 The same key and IV should be used at the decryption end. The code for AES 256 in python to encrypt audio files is, Concept. Generate key and IV using random functions. Open the file and read it. This will return bytes as the algorithm requires the data to be in the form of bytes. Encrypt it using the encrypt function of the pycrypto library. Oct 17, 2013  Python also provides a pleasant framework for prototyping and experimentation with cryptographic algorithms; thanks to its arbitrary-length integers, public key algorithms are easily implemented. As of PyCrypto 2.1.0, PyCrypto provides an easy-to-use random number generator.

PyCryptoDome vs PyCrypto vs None. When installing, no cryptography package is provided by default. Use ml-cryptopycryptodome or ml-cryptopycrypto to ensure one is installed or use the default if you know you have one installed; As pycrypto is dead, prefer using pycryptodome and expect some issues (The main one is encrypted ssh private keys.

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• AES-128, AES-192 and AES-256 implementations in pure python (very slow, butworks).Results have been tested against the NIST standard (http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf)
• CBC mode for AES with PKCS#7 padding (now also PCBC, CFB, OFB and CTR thanks to @righthandabacus!)
• encrypt and decrypt functions for protecting arbitrary data with apassword

Note: this implementation is not resistant to side channel attacks.

Although this is an exercise, the encrypt and decrypt functions shouldprovide reasonable security to encrypted messages. It ensures the data iskept secret (using AES), blocks are encrypted together (CBC), the samemessage encrypted twice will have different ciphertexts (salt), the ciphertexthasn't been tampered with (HMAC) and the key has some defense against brute-force(PBKDF2).

The algorithm is as follows:

1. 16 random bytes of salt are extracted from the system's secure random numbergenerator (usually /dev/urandom)>

2. The given master key is stretched and expanded by PKBDF2-HMAC(SHA256) usingthe salt from 1), to generate the AES key, HMAC key and IV (initializationvector for CBC).

3. The given message is encrypted with AES-128 using the AES key and IV fromstep 2), in CBC mode and PKCS#7 padding.

4. A HMAC-SHA256 is generated from the concatenation of the salt from 1) andthe ciphertext from 3).

   root@node2 # gpg -sign-key 20B43A0Cpub 2048R/20B43A0C created: 2018-12-09 expires: never usage: SCtrust: unknown validity: unknownsub 2048R/3832437D created: 2018-12-09 expires: never usage: E unknown (1). Amit Kumar (Amit Kumar's Inbox) pub 2048R/613099BE created: 2018-12-09 expires: never usage: SCtrust: unknown validity: unknownPrimary key fingerprint: 8D09 5E6D 57BF 81AF D356 3190 FD29 32DC 6130 99BEAmit Kumar (Amit Kumar's Inbox) Are you sure that you want to sign this key with yourkey 'Deepak Prasad (Deepak Prasad's Inbox) ' (20B43A0C)Really sign? (y/N) yYou need a passphrase to unlock the secret key foruser: 'Deepak Prasad (Deepak Prasad's Inbox) '2048-bit RSA key, ID 20B43A0C, created 2018-12-09The following output shows that Deepak’s key is 2,048 bits long, uses RSA encryption (R), and has a key ID of 20B43A0C on node2. Deepak Prasad (Deepak Prasad's Inbox) pub 2048R/20B43A0C created: 2018-12-09 expires: never usage: SCtrust: unknown validity: unknownPrimary key fingerprint: FBC3 2F86 D80D 977D 040D F252 56BE E2ED 20B4 3A0CDeepak Prasad (Deepak Prasad's Inbox) Are you sure that you want to sign this key with yourkey 'Amit Kumar (Amit Kumar's Inbox) ' (613099BE)Really sign? Generate public key from private gpg. root@node1 # gpg -sign-key 613099BEpub 2048R/613099BE created: 2018-12-09 expires: never usage: SCtrust: unknown validity: unknownsub 2048R/B8AE9FEB created: 2018-12-09 expires: never usage: E unknown (1).

5. The final ciphertext is HMAC + salt + ciphertext.

Security overview:

Python Pycrypto Generate Key 2019 Download

• The random salt ensures the same message will map to different ciphertexts.

• The HMAC ensures the integrity of both the entire ciphertext and the PKBDF2salt; encrypt-then-mac prevents attacks like Padding Oracle.

• Bytes from keys, iv and salt are not reused in different algorithms.

• PBKDF2 key stretching allows for relatively weak passwords to be used as AESkeys and be moderately resistant to brute-force, but sacrificing performance.