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PKCS#5 padding is identical to PKCS#7 padding, except that it has only been defined for block ciphers that use a 64-bit (8-byte) block size. In practice, the two can be used interchangeably. The maximum block size is 255, as it is the biggest number a byte can contain.
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.
The attack uses the padding as an oracle. [4] [5] PKCS #1 was subsequently updated in the release 2.0 and patches were issued to users wishing to continue using the old version of the standard. [3] However, the vulnerable padding scheme remains in use and has resulted in subsequent attacks:
The zero padding in this step is important for step 5. D n = E n−1 XOR P. Exclusive-OR E n−1 with P to create D n. For the first M bits of the block, this is equivalent to CBC mode; the first M bits of the previous block's ciphertext, E n−1, are XORed with the M bits of plaintext of the last plaintext block.
Adaptive-chosen-ciphertext attacks were perhaps considered to be a theoretical concern, but not to have been be manifested in practice, until 1998, when Daniel Bleichenbacher (then of Bell Laboratories) demonstrated a practical attack against systems using RSA encryption in concert with the PKCS#1 v1.5 encoding function, including a version of the Secure Sockets Layer (SSL) protocol used by ...
An initialization vector (IV) or starting variable (SV) [5] is a block of bits that is used by several modes to randomize the encryption and hence to produce distinct ciphertexts even if the same plaintext is encrypted multiple times, without the need for a slower re-keying process.
In cryptography, Optimal Asymmetric Encryption Padding (OAEP) is a padding scheme often used together with RSA encryption.OAEP was introduced by Bellare and Rogaway, [1] and subsequently standardized in PKCS#1 v2 and RFC 2437.
The attack relies on having a "padding oracle" who freely responds to queries about whether a message is correctly padded or not. The information could be directly given, or leaked through a side-channel. The earliest well-known attack that uses a padding oracle is Bleichenbacher's attack of 1998, which attacks RSA with PKCS #1 v1.5 padding. [1]