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Questions tagged [oaep]

Optimal Asymmetric Encryption Padding is a padding scheme which has been standardized in [PKCS #1v29](http://www.emc.com/collateral/white-papers/h11300-pkcs-1v2-2-rsa-cryptography-standard-wp.pdf) and 8RFC 2437](http://tools.ietf.org/html/rfc2437). OAEP is often used in combination with RSA encryption.

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1answer
67 views

Does RSA key transmit with OAEP insecure?

In the Key encapsulation article of Wikipedia, the RSA-KEM is described shortly, as follows; Generate a random element $1<m<n$ then drive your symmetric key by $M=\text{KDF}(m)$ Then compute ...
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consequences of using fixed values with OAEP

With DSA / ECDSA using a fixed $k$ means the private key can be trivially easily calculated from two different signatures. To remedy this RFC6979 Deterministic Usage of the Digital Signature Algorithm ...
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Preferred SHA-2 hash algorithm for MGF1 in RSA

Does it make any difference to the security and efficiency if we use SHA-256 or SHA-512 for the Mask Generation Function MGF1 that generates the masking / padding within the OAEP encryption scheme and ...
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Probabilistic padding to avoid Håstad’s Broadcast Attack

Can someone explain why probabilistic padding like OAEP is particularly useful for avoiding Håstad’s Broadcast Attack? I don't really get the reason why.
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OAEP Security: PKCS#1 v1.5 vs SHA1 vs SHA256

I'm looking at two major RSA encryption standards: PKCS#1 ver. 1.5 RSA OAEP The second one can use different hashing functions to create a hash of encoding parameters and then verify the hash at ...
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1answer
347 views

RSA-OAEP Padding scheme

Honestly I'm really confused about padding in RSA scheme. I don't study computer science, and I'm a beginner learning cryptography (self-taught). Can anyone give me suggestions?
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What are the uses of arbitrary length output hashes (other than OAEP)?

Functions such as SHA-3 from the Keccak family allow for a hash of arbitrary length output. These functions are (according to Wikipedia) useful for practical, lightweight applications. I know that ...
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1answer
84 views

OAEP security with variable length hash function

I'm implementing a hobby cryptosystem for fun and to increase my knowledge on the subject, and I was wondering if the OAEP construct was still sufficient as an all-or-nothing-transform if variable ...
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2answers
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If OAEP is introducing randomness to encryption how could be ciphertext decrypted?

I was studying OAEP and see we introduce a random value $r$ when computing the padding. See the figure below from Wikipedia So if we are adding randomness to encryption, how could this ciphertext be ...
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OAEP Hash function truncation

I am using OAEP in a project and I want the resulting number of bits (n) to be 288 bits. Most of the implementations online seem to be for 1024 bits and using SHA-256 and I was wondering if truncating ...
3
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1answer
154 views

Is OAEP needed when encrypting a session (random) key using RSA?

My question is two parts: when encrypting a session key which is used to encrypt bulk data using a block cipher for example, is padding with OAEP really needed [i'm assuming the key is generated ...
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Is Bouncycastle RSA+OAEP implementation vulnerable to Manger’s attack?

I have written a code to encrypt a plaintext as below. Here I am using bouncycastle crypto provider and referring to the RSA+OAEP for that. ...
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371 views

What is the reason for length differences in RSA?

In NIST FIPS 186-4, "digital signature algorithm", the minimal length allowed is 1024 bit (page 22). On the contrary, in NIST SP800-56B, page 63, RSA-OAEP encryption, the minimal length is 2048. Why ...
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1answer
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What's the point of OAEP?

I can't seem to wrap my head around what benefit OAEP provides (specifically with RSA). Lets consider really small numbers for a moment. If the random source in the padding algorithm gave a random ...
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OAEP Cryptanalysis with broken hash

Keeping OAEP Cryptanalysis in mind, about the inability to get to $M_1$ or $M_2$ given $\operatorname{OAEP}(M_1) \oplus \operatorname{OAEP}(M_2)$. Would it be possible to get to $M_1$ or $M_2$, given ...
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1answer
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Brute-force attack on OAEP

Assume $M_1$ is $\operatorname{OAEP}$ padded and encrypted and the ciphertext is 1024 bytes as an example. If an adversary somehow gets around the encryption and manages to get half of the bits of $\...
2
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1answer
147 views

OAEP Cryptanalysis

If $M_1$ and $M_2$ are $\operatorname{OAEP}$ padded, encrypted and sent and an adversary somehow manages to get around the encryption and retrieve $\operatorname{OAEP}(M_1) \oplus \operatorname{OAEP}(...
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Distinguish between cipher-texts of text-book RSA and RSA/OAEP

Is there is a possibility to identify from cipher-text that, this is been encrypted using a text-book RSA or RSA with OAEP padding. (By looking at the cipher-text only) ?
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1answer
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Use of OAEP in RSA Encryption

I am working on creating an RSA Algorithm and learned that OAEP is a padding scheme that is commonly used before encrypting using RSA. Is this step necessary? Will it harm the integrity/security of ...
3
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1answer
224 views

Role of lHash field in RSAES-OAEP

The RSA encryption padding of RSAES-OAEP has a lHash field set to the hash of a label. That label is typically the empty string, or some public description of the intended use of the message. Does ...
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2answers
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Is RSA-OAEP deprecated?

I need asymmetric pub/private keypair encryption in JavaScript. Web browsers support RSA-OAEP, which works exactly as I need. But there is a table which lists supported algorithms for web crypto at ...
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1answer
376 views

Why is the seed masked in OAEP

In the OAEP padding/armoring scheme for RSA encryption, the seed used is masked (with the masked data block) in the end. Why is that necessary, since the seed is random anyway?
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1answer
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Zero byte header in RSA-OAEP vs. RSA-PSS

PKCS#1 v2.1/RFC3437 defines the OAEP padding mode for encryption and the PSS for signature padding. Both schemes are based on the generic constructions not specifically tailored to RSA by Rogaway &...
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1answer
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Security effects of the seed's length in OAEP

In the OAEP scheme for asymetric encryption padding a random seed is used, whose length can be chosen. The paper which introduced OAEP in 1994 just states, that the seed's length $k_0$ should be ...
2
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1answer
499 views

What does the mask generation function in PKCS#1 output if the generated mask is shorter than the specified mask length?

I am implementing RSA-OAEP with the mask generation function as specified in PKCS #1. It says after producing the variable T to "output the leading maskLen octets of T as the octet string mask". ...
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What is the maximum size of the plaintext message for RSA OAEP?

OAEP is an important technique used to strengthen RSA. However, using OAEP (or any technique that adds randomness) reduces the size of plaintexts that can be encrypted. Assume for instance that OAEP ...
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1answer
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Generation of random data for EME-OAEP

I'm using my own code to communicate with another party that's specified PKCS#1 V2.1 EME-OAEP encoding, with SHA-1 as the hash function. There are two places where random data is used in encoding a ...
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1answer
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why did oaep change from pkcs1 v2.0 and v2.1?

In PKCS1 v2.1 the OAEP output is prepending with a null byte. Quoting RFC3447, ...
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1answer
508 views

In PKCS#1 V2.2, should MGF be based on the same hash function that RSA-OAEP-ENCRYPT uses?

In Section 7.1.1 of PKCS#1 v2.2 there are two options for RSAES-OAEP-Encrypt given: Hash MGF Appendix B.2.1 of the same document states that MGF1 is based on a hash function. Is MGF1 based on the ...
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Why is padding the plaintext with a random string before encryption worse than OAEP / PKCS#7?

I'm reading about OAEP / PKCS padding used for PGP to turn deterministic algorithms like RSA from deterministic encryption to probabilistic encryption (randomness in the resulting output). That way ...
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1answer
94 views

Should we use exponent 3 in RSA-OAEP?

As I understand it the proof that RSA-OAEP is secure in the random oracle model is much tighter for exponent 3. Does that mean that exponent 3 should be chosen?
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1answer
407 views

Is RSA encryption without padding secure with NIST Key Establishment schemes?

NIST SP800-56B standard (addressing IFC-based Key Establishment schemes) defines some key establishment (KE) schemes using the RSASVE primitive in which the common secret $Z$ is encrypted with RSA-EP ...
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1answer
424 views

Can RSA with padding detect all errors in ciphertext?

I'm new in cryptography and there are a couple of things that i'm not sure if i understand correctly. First, when using padding (PKCS or OAEP), if the chiphertext has errors in transmission we'll we ...
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1answer
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RSA-OAEP: How does it work?

I was looking at this image about OAEP: ..and was wondering what was happening here. We have a data block DB which consists of: ...
3
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1answer
432 views

Does rsa-oaep provide or not plaintext integrity in addition to confidentiality?

My own understanding (possibly wrong of course) of RSA-OAEP encryption scheme is that it provides plaintext integrity (in addition to confidentiality) due to MGF function which for encryption ...
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1answer
2k views

RSA Optimal Asymmetric Encryption Padding Beginner

I'm new to the OAEP scheme. I learn it from the Wikipedia page. Link The page does not explain a proper setup for of the system. So I'm not sure if the output of the padding scheme which contains ...
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0answers
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Is using same key pair for both encryption and signing secure in RSA [duplicate]

In GPG, we can use same key pair for encryption and signing. Can't/Shouldn't we do this in RSA. I am using RSAES-OAEP and RSASSA-PSS, not raw RSA btw.
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Why not use OAEP for signatures?

There seems to be a distinct lack of implementations of RSA signatures using OAEP to pad the digest. Other than the old, funky, padding schemes, it's PSS all the way. PSS seems to have the whiff of ...
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1answer
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Secure ElGamal with OAEP

Is it possible to make ElGamal IND-CCA2 using OAEP or OAEP+? (OAEP+ from: "OAEP Reconsiderd" by Shoup) The reason I ask is that I recently answered this question and it came to my mind that OAEP or ...
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0answers
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Is RSA-OAEP secure when e=3? [duplicate]

Is RSA-OAEP secure when the exponent is equal to 3?
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1answer
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Strength of RSA with OAEP

In our current system we use an encryption solution based on RSA with OAEP padding. Key size is optional but default 2048. What is the general strength of RSA with OAEP? Are there know attacks that ...
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362 views

Defending hybrid encryption schemes against padding oracle attacks

I intend to use a generic integrated/hybrid encryption scheme for transmitting information between a client and a server. Key encapsulation: a 128-bit symmetric key is generated and asymmetrically ...
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2answers
886 views

Selection of cryptographic functions for OAEP

I can't understand how the "cryptographic functions" are to be selected RSA + OAEP which are used in OAEP. How to choose these "cryptographic functions"(G and H)?
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Questions about OAEP for RSA

I have two questions about OAEP for RSA. How are the number of bits to pad with 0 chosen? For example, if I'm sending a 255 byte message with RSA-2048 I have 8 unused bits (1 byte). Should I split ...
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159 views

partial-domain permutation and strong assumption

Quoting "Verified Security of Redundancy-Free Encryption from Rabin and RSA", Chapter 2 (on page 4): OAEP was proved IND-CCA-secure by Fujisaki et al. [28] under the assumption that the underlying ...
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1answer
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How does OAEP improve the security of RSA?

The heart of OAEP algorithm used for RSA encryption are the cryptographic hash functions $H$ and $G$. Does everybody (so also an adversary) know these functions? If YES: How does it help the ...
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1answer
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Is OAEP reversible?

Given nothing more than some integer $m =$ OAEP($M$), is it possible to recover the original plaintext $M$? In other words, without being given the hash functions or the random string used for ...