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Many padding schemes are based on appending predictable data to the final block. For example, the pad could be derived from the total length of the message. This kind of padding scheme is commonly applied to hash algorithms that use the Merkle–Damgård construction such as MD-5, SHA-1, and SHA-2 family such as SHA-224, SHA-256, SHA-384, SHA ...
However, the original scheme was proved in the random oracle model to be IND-CCA2 secure when OAEP is used with the RSA permutation using standard encryption exponents, as in the case of RSA-OAEP. [2] An improved scheme (called OAEP+) that works with any trapdoor one-way permutation was offered by Victor Shoup to solve this problem. [3]
However, the vulnerable padding scheme remains in use and has resulted in subsequent attacks: Bardou et al. (2012) find that several models of PKCS 11 tokens still use the v1.5 padding scheme for RSA. They propose an improved version of Bleichenbacher's attack that requires fewer messages.
PKCS Standards Summary; Version Name Comments PKCS #1: 2.2: RSA Cryptography Standard [1]: See RFC 8017. Defines the mathematical properties and format of RSA public and private keys (ASN.1-encoded in clear-text), and the basic algorithms and encoding/padding schemes for performing RSA encryption, decryption, and producing and verifying signatures.
Standards such as PKCS#1 have been carefully designed to securely pad messages prior to RSA encryption. Because these schemes pad the plaintext m with some number of additional bits, the size of the un-padded message M must be somewhat smaller. RSA padding schemes must be carefully designed so as to prevent sophisticated attacks that may be ...
IFES (Integer Factorization Encryption Scheme): Essentially RSA encryption with Optimal Asymmetric Encryption Padding (OAEP). DL/ECIES (Discrete Logarithm/Elliptic Curve Integrated Encryption Scheme): Essentially the "DHAES" variant of ElGamal encryption. IFES-EPOC (Integer Factorization Encryption Scheme, EPOC version)
There are some Public Key encryption schemes that allow keyword search, [1] [2] [3] however these schemes all require search time linear in the database size. If the database entries were encrypted with a deterministic scheme and sorted, then a specific field of the database could be retrieved in logarithmic time.
Mask generation functions were first proposed as part of the specification for padding in the RSA-OAEP algorithm. The OAEP algorithm required a cryptographic hash function that could generate an output equal in size to a "data block" whose length was proportional to arbitrarily sized input message.