{"id":54924,"date":"2020-01-08T00:00:00","date_gmt":"2020-01-07T21:00:00","guid":{"rendered":"https:\/\/prohoster.info\/blog\/blog_prohoster\/predlozhen-metod-opredeleniya-kollizij-v-sha-1-prigodnyj-dlya-ataki-na-pgp"},"modified":"2020-02-18T14:02:59","modified_gmt":"2020-02-18T11:02:59","slug":"predlozhen-metod-opredeleniya-kollizij-v-sha-1-prigodnyj-dlya-ataki-na-pgp","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/news\/predlozhen-metod-opredeleniya-kollizij-v-sha-1-prigodnyj-dlya-ataki-na-pgp","title":{"rendered":"A method for collision detection in SHA-1 has been proposed, suitable for attacking PGP.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Researchers from the French National Institute for Research in Computer Science and Automation (INRIA) and Nanyang Technological University (Singapore) have presented a method of attack Shambles<\/a><\/noindex> (PDF<\/a><\/noindex>), which is touted as the first practical implementation of an attack on the SHA-1 algorithm that can be used to create fake digital signatures for PGP and GnuPG. The researchers believe that all practical attacks on MD5 can now also be applied to SHA-1, although they still require significant resources for execution.<\/p>\n

The method is based on conducting a collision attack with a predefined prefix<\/a><\/noindex>, allowing for two arbitrary data sets to find extensions, where attaching them will result in colliding sets, for which the use of the SHA-1 algorithm will lead to the formation of the same resulting hash. In other words, for two existing documents, it is possible to compute two extensions, and if one is attached to the first document and the other to the second, the resulting SHA-1 hashes for these files will be the same.<\/p>\n

The new method differs from previously proposed similar techniques by improving the efficiency of collision searches and demonstrating practical applicability for attacks on PGP. In particular, the researchers managed to prepare two public PGP keys of different sizes (RSA-8192 and RSA-6144) with differing user identifiers and certificates that cause SHA-1 collisions. The first key<\/a><\/noindex> included the victim's identifier, while the second key<\/a><\/noindex> contained the attacker's name and image. Thanks to the collision, the identifying certificate that included the key and the attacker's image had the same SHA-1 hash as the identification certificate that included the key and the victim's name. <\/p>\n

The attacker could request a digital signature for their key and image from an external certification authority, then transfer the digital signature for the victim's key. The digital signature remains valid due to the collision and the certification of the attacker's key by the certification authority, allowing the attacker to take control of the key bearing the victim's name (since the SHA-1 hashes for both keys match). As a result, the attacker can impersonate the victim and sign any document on their behalf.<\/p>\n

The attack is still quite costly, but is now affordable for intelligence agencies and large corporations. The costs for a simple collision search using the cheaper NVIDIA GTX 970 GPU amounted to $11,000, while for searching for a collision with a specified prefix it was $45,000 (for comparison, in 2012, the cost of finding a collision in SHA-1 was estimated at $2 million, and in 2015 it was $700,000). To carry out a practical attack on PGP, two months of computation were required, involving 900 NVIDIA GTX 1060 GPUs, the rental of which cost researchers $75,000.<\/p>\n

The method proposed by researchers for detecting collisions is about 10 times more effective than previous achievements\u2014the complexity level for calculating a collision has been reduced to 261.2 operations, instead of 264.7, and collisions with a specified prefix to 263.4 operations instead of 267.1. Researchers recommend transitioning from SHA-1 to using SHA-256 or SHA-3 as soon as possible, as they predict that by 2025 the cost of conducting an attack will drop to $10,000.<\/p>\n

The developers of GnuPG were notified about the issue on October 1 (CVE-2019-14855) and on November 25, in the release of GnuPG 2.2.18, took measures to block problematic certificates\u2014all digital identifying signatures using SHA-1 created after January 19 last year are now considered invalid. CAcert, one of the main certification authorities for PGP keys, plans to switch to using more secure hash functions for key certification. In response to information about the new attack method, OpenSSL developers decided to disable SHA-1 at the proposed default first security level (SHA-1 can no longer be used for certificates and digital signatures during connection negotiations).<\/p>\n

<\/a><\/noindex><\/p>\n

Source: opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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